JAL-2738 use GeneLocus extends DBRefEntry to hold chromosomal mappings
[jalview.git] / src / jalview / analysis / AlignmentUtils.java
index 37f225c..0bc8180 100644 (file)
@@ -22,7 +22,6 @@ package jalview.analysis;
 
 import static jalview.io.gff.GffConstants.CLINICAL_SIGNIFICANCE;
 
-import jalview.api.DBRefEntryI;
 import jalview.datamodel.AlignedCodon;
 import jalview.datamodel.AlignedCodonFrame;
 import jalview.datamodel.AlignedCodonFrame.SequenceToSequenceMapping;
@@ -30,17 +29,20 @@ import jalview.datamodel.Alignment;
 import jalview.datamodel.AlignmentAnnotation;
 import jalview.datamodel.AlignmentI;
 import jalview.datamodel.DBRefEntry;
+import jalview.datamodel.GeneLociI;
 import jalview.datamodel.IncompleteCodonException;
 import jalview.datamodel.Mapping;
 import jalview.datamodel.Sequence;
 import jalview.datamodel.SequenceFeature;
 import jalview.datamodel.SequenceGroup;
 import jalview.datamodel.SequenceI;
-import jalview.io.gff.SequenceOntologyFactory;
+import jalview.datamodel.features.SequenceFeatures;
+import jalview.io.gff.Gff3Helper;
 import jalview.io.gff.SequenceOntologyI;
 import jalview.schemes.ResidueProperties;
 import jalview.util.Comparison;
 import jalview.util.DBRefUtils;
+import jalview.util.IntRangeComparator;
 import jalview.util.MapList;
 import jalview.util.MappingUtils;
 import jalview.util.StringUtils;
@@ -51,7 +53,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
@@ -61,6 +62,7 @@ import java.util.Map;
 import java.util.Map.Entry;
 import java.util.NoSuchElementException;
 import java.util.Set;
+import java.util.SortedMap;
 import java.util.TreeMap;
 
 /**
@@ -72,23 +74,30 @@ import java.util.TreeMap;
  */
 public class AlignmentUtils
 {
+  private static final int CODON_LENGTH = 3;
 
   private static final String SEQUENCE_VARIANT = "sequence_variant:";
-  private static final String ID = "ID";
+
+  /*
+   * the 'id' attribute is provided for variant features fetched from
+   * Ensembl using its REST service with JSON format 
+   */
+  public static final String VARIANT_ID = "id";
 
   /**
    * A data model to hold the 'normal' base value at a position, and an optional
    * sequence variant feature
    */
-  static class DnaVariant
+  static final class DnaVariant
   {
-    String base;
+    final String base;
 
     SequenceFeature variant;
 
     DnaVariant(String nuc)
     {
       base = nuc;
+      variant = null;
     }
 
     DnaVariant(String nuc, SequenceFeature var)
@@ -96,6 +105,20 @@ public class AlignmentUtils
       base = nuc;
       variant = var;
     }
+
+    public String getSource()
+    {
+      return variant == null ? null : variant.getFeatureGroup();
+    }
+
+    /**
+     * toString for aid in the debugger only
+     */
+    @Override
+    public String toString()
+    {
+      return base + ":" + (variant == null ? "" : variant.getDescription());
+    }
   }
 
   /**
@@ -108,7 +131,7 @@ public class AlignmentUtils
    */
   public static AlignmentI expandContext(AlignmentI core, int flankSize)
   {
-    List<SequenceI> sq = new ArrayList<SequenceI>();
+    List<SequenceI> sq = new ArrayList<>();
     int maxoffset = 0;
     for (SequenceI s : core.getSequences())
     {
@@ -161,10 +184,12 @@ public class AlignmentUtils
         }
       }
       // TODO use Character.toLowerCase to avoid creating String objects?
-      char[] upstream = new String(ds.getSequence(s.getStart() - 1
-              - ustream_ds, s.getStart() - 1)).toLowerCase().toCharArray();
-      char[] downstream = new String(ds.getSequence(s_end - 1, s_end
-              + dstream_ds)).toLowerCase().toCharArray();
+      char[] upstream = new String(ds
+              .getSequence(s.getStart() - 1 - ustream_ds, s.getStart() - 1))
+                      .toLowerCase().toCharArray();
+      char[] downstream = new String(
+              ds.getSequence(s_end - 1, s_end + dstream_ds)).toLowerCase()
+                      .toCharArray();
       char[] coreseq = s.getSequence();
       char[] nseq = new char[offset + upstream.length + downstream.length
               + coreseq.length];
@@ -179,8 +204,8 @@ public class AlignmentUtils
       System.arraycopy(upstream, 0, nseq, p, upstream.length);
       System.arraycopy(coreseq, 0, nseq, p + upstream.length,
               coreseq.length);
-      System.arraycopy(downstream, 0, nseq, p + coreseq.length
-              + upstream.length, downstream.length);
+      System.arraycopy(downstream, 0, nseq,
+              p + coreseq.length + upstream.length, downstream.length);
       s.setSequence(new String(nseq));
       s.setStart(s.getStart() - ustream_ds);
       s.setEnd(s_end + downstream.length);
@@ -236,7 +261,7 @@ public class AlignmentUtils
   public static Map<String, List<SequenceI>> getSequencesByName(
           AlignmentI al)
   {
-    Map<String, List<SequenceI>> theMap = new LinkedHashMap<String, List<SequenceI>>();
+    Map<String, List<SequenceI>> theMap = new LinkedHashMap<>();
     for (SequenceI seq : al.getSequences())
     {
       String name = seq.getName();
@@ -245,7 +270,7 @@ public class AlignmentUtils
         List<SequenceI> seqs = theMap.get(name);
         if (seqs == null)
         {
-          seqs = new ArrayList<SequenceI>();
+          seqs = new ArrayList<>();
           theMap.put(name, seqs);
         }
         seqs.add(seq);
@@ -272,8 +297,8 @@ public class AlignmentUtils
       return false;
     }
 
-    Set<SequenceI> mappedDna = new HashSet<SequenceI>();
-    Set<SequenceI> mappedProtein = new HashSet<SequenceI>();
+    Set<SequenceI> mappedDna = new HashSet<>();
+    Set<SequenceI> mappedProtein = new HashSet<>();
 
     /*
      * First pass - map sequences where cross-references exist. This include
@@ -307,9 +332,9 @@ public class AlignmentUtils
    * @return
    */
   protected static boolean mapProteinToCdna(
-          final AlignmentI proteinAlignment,
-          final AlignmentI cdnaAlignment, Set<SequenceI> mappedDna,
-          Set<SequenceI> mappedProtein, boolean xrefsOnly)
+          final AlignmentI proteinAlignment, final AlignmentI cdnaAlignment,
+          Set<SequenceI> mappedDna, Set<SequenceI> mappedProtein,
+          boolean xrefsOnly)
   {
     boolean mappingExistsOrAdded = false;
     List<SequenceI> thisSeqs = proteinAlignment.getSequences();
@@ -338,9 +363,8 @@ public class AlignmentUtils
          * Don't map non-xrefd sequences more than once each. This heuristic
          * allows us to pair up similar sequences in ordered alignments.
          */
-        if (!xrefsOnly
-                && (mappedProtein.contains(aaSeq) || mappedDna
-                        .contains(cdnaSeq)))
+        if (!xrefsOnly && (mappedProtein.contains(aaSeq)
+                || mappedDna.contains(cdnaSeq)))
         {
           continue;
         }
@@ -374,7 +398,7 @@ public class AlignmentUtils
    * Answers true if the mappings include one between the given (dataset)
    * sequences.
    */
-  public static boolean mappingExists(List<AlignedCodonFrame> mappings,
+  protected static boolean mappingExists(List<AlignedCodonFrame> mappings,
           SequenceI aaSeq, SequenceI cdnaSeq)
   {
     if (mappings != null)
@@ -393,7 +417,8 @@ public class AlignmentUtils
   /**
    * Builds a mapping (if possible) of a cDNA to a protein sequence.
    * <ul>
-   * <li>first checks if the cdna translates exactly to the protein sequence</li>
+   * <li>first checks if the cdna translates exactly to the protein
+   * sequence</li>
    * <li>else checks for translation after removing a STOP codon</li>
    * <li>else checks for translation after removing a START codon</li>
    * <li>if that fails, inspect CDS features on the cDNA sequence</li>
@@ -415,8 +440,9 @@ public class AlignmentUtils
      * String objects.
      */
     final SequenceI proteinDataset = proteinSeq.getDatasetSequence();
-    char[] aaSeqChars = proteinDataset != null ? proteinDataset
-            .getSequence() : proteinSeq.getSequence();
+    char[] aaSeqChars = proteinDataset != null
+            ? proteinDataset.getSequence()
+            : proteinSeq.getSequence();
     final SequenceI cdnaDataset = cdnaSeq.getDatasetSequence();
     char[] cdnaSeqChars = cdnaDataset != null ? cdnaDataset.getSequence()
             : cdnaSeq.getSequence();
@@ -428,7 +454,7 @@ public class AlignmentUtils
     /*
      * cdnaStart/End, proteinStartEnd are base 1 (for dataset sequence mapping)
      */
-    final int mappedLength = 3 * aaSeqChars.length;
+    final int mappedLength = CODON_LENGTH * aaSeqChars.length;
     int cdnaLength = cdnaSeqChars.length;
     int cdnaStart = cdnaSeq.getStart();
     int cdnaEnd = cdnaSeq.getEnd();
@@ -440,14 +466,14 @@ public class AlignmentUtils
      */
     if (cdnaLength != mappedLength && cdnaLength > 2)
     {
-      String lastCodon = String.valueOf(cdnaSeqChars, cdnaLength - 3, 3)
-              .toUpperCase();
-      for (String stop : ResidueProperties.STOP)
+      String lastCodon = String.valueOf(cdnaSeqChars,
+              cdnaLength - CODON_LENGTH, CODON_LENGTH).toUpperCase();
+      for (String stop : ResidueProperties.STOP_CODONS)
       {
         if (lastCodon.equals(stop))
         {
-          cdnaEnd -= 3;
-          cdnaLength -= 3;
+          cdnaEnd -= CODON_LENGTH;
+          cdnaLength -= CODON_LENGTH;
           break;
         }
       }
@@ -457,14 +483,13 @@ public class AlignmentUtils
      * If lengths still don't match, try ignoring start codon.
      */
     int startOffset = 0;
-    if (cdnaLength != mappedLength
-            && cdnaLength > 2
-            && String.valueOf(cdnaSeqChars, 0, 3).toUpperCase()
+    if (cdnaLength != mappedLength && cdnaLength > 2
+            && String.valueOf(cdnaSeqChars, 0, CODON_LENGTH).toUpperCase()
                     .equals(ResidueProperties.START))
     {
-      startOffset += 3;
-      cdnaStart += 3;
-      cdnaLength -= 3;
+      startOffset += CODON_LENGTH;
+      cdnaStart += CODON_LENGTH;
+      cdnaLength -= CODON_LENGTH;
     }
 
     if (translatesAs(cdnaSeqChars, startOffset, aaSeqChars))
@@ -472,8 +497,9 @@ public class AlignmentUtils
       /*
        * protein is translation of dna (+/- start/stop codons)
        */
-      MapList map = new MapList(new int[] { cdnaStart, cdnaEnd }, new int[]
-      { proteinStart, proteinEnd }, 3, 1);
+      MapList map = new MapList(new int[] { cdnaStart, cdnaEnd },
+              new int[]
+              { proteinStart, proteinEnd }, CODON_LENGTH, 1);
       return map;
     }
 
@@ -504,16 +530,17 @@ public class AlignmentUtils
     int aaPos = 0;
     int dnaPos = cdnaStart;
     for (; dnaPos < cdnaSeqChars.length - 2
-            && aaPos < aaSeqChars.length; dnaPos += 3, aaPos++)
+            && aaPos < aaSeqChars.length; dnaPos += CODON_LENGTH, aaPos++)
     {
-      String codon = String.valueOf(cdnaSeqChars, dnaPos, 3);
+      String codon = String.valueOf(cdnaSeqChars, dnaPos, CODON_LENGTH);
       final String translated = ResidueProperties.codonTranslate(codon);
 
       /*
        * allow * in protein to match untranslatable in dna
        */
       final char aaRes = aaSeqChars[aaPos];
-      if ((translated == null || "STOP".equals(translated)) && aaRes == '*')
+      if ((translated == null || ResidueProperties.STOP.equals(translated))
+              && aaRes == '*')
       {
         continue;
       }
@@ -542,10 +569,11 @@ public class AlignmentUtils
     {
       return true;
     }
-    if (dnaPos == cdnaSeqChars.length - 3)
+    if (dnaPos == cdnaSeqChars.length - CODON_LENGTH)
     {
-      String codon = String.valueOf(cdnaSeqChars, dnaPos, 3);
-      if ("STOP".equals(ResidueProperties.codonTranslate(codon)))
+      String codon = String.valueOf(cdnaSeqChars, dnaPos, CODON_LENGTH);
+      if (ResidueProperties.STOP
+              .equals(ResidueProperties.codonTranslate(codon)))
       {
         return true;
       }
@@ -623,10 +651,9 @@ public class AlignmentUtils
    * @param preserveUnmappedGaps
    * @param preserveMappedGaps
    */
-  public static void alignSequenceAs(SequenceI alignTo,
-          SequenceI alignFrom, AlignedCodonFrame mapping, String myGap,
-          char sourceGap, boolean preserveMappedGaps,
-          boolean preserveUnmappedGaps)
+  public static void alignSequenceAs(SequenceI alignTo, SequenceI alignFrom,
+          AlignedCodonFrame mapping, String myGap, char sourceGap,
+          boolean preserveMappedGaps, boolean preserveUnmappedGaps)
   {
     // TODO generalise to work for Protein-Protein, dna-dna, dna-protein
 
@@ -642,15 +669,16 @@ public class AlignmentUtils
     int toOffset = alignTo.getStart() - 1;
     int sourceGapMappedLength = 0;
     boolean inExon = false;
-    final char[] thisSeq = alignTo.getSequence();
-    final char[] thatAligned = alignFrom.getSequence();
-    StringBuilder thisAligned = new StringBuilder(2 * thisSeq.length);
+    final int toLength = alignTo.getLength();
+    final int fromLength = alignFrom.getLength();
+    StringBuilder thisAligned = new StringBuilder(2 * toLength);
 
     /*
      * Traverse the 'model' aligned sequence
      */
-    for (char sourceChar : thatAligned)
+    for (int i = 0; i < fromLength; i++)
     {
+      char sourceChar = alignFrom.getCharAt(i);
       if (sourceChar == sourceGap)
       {
         sourceGapMappedLength += ratio;
@@ -690,9 +718,9 @@ public class AlignmentUtils
        */
       int intronLength = 0;
       while (basesWritten + toOffset < mappedCodonEnd
-              && thisSeqPos < thisSeq.length)
+              && thisSeqPos < toLength)
       {
-        final char c = thisSeq[thisSeqPos++];
+        final char c = alignTo.getCharAt(thisSeqPos++);
         if (c != myGapChar)
         {
           basesWritten++;
@@ -718,7 +746,7 @@ public class AlignmentUtils
             int gapsToAdd = calculateGapsToInsert(preserveMappedGaps,
                     preserveUnmappedGaps, sourceGapMappedLength, inExon,
                     trailingCopiedGap.length(), intronLength, startOfCodon);
-            for (int i = 0; i < gapsToAdd; i++)
+            for (int k = 0; k < gapsToAdd; k++)
             {
               thisAligned.append(myGapChar);
             }
@@ -746,9 +774,9 @@ public class AlignmentUtils
      * At end of model aligned sequence. Copy any remaining target sequence, optionally
      * including (intron) gaps.
      */
-    while (thisSeqPos < thisSeq.length)
+    while (thisSeqPos < toLength)
     {
-      final char c = thisSeq[thisSeqPos++];
+      final char c = alignTo.getCharAt(thisSeqPos++);
       if (c != myGapChar || preserveUnmappedGaps)
       {
         thisAligned.append(c);
@@ -821,8 +849,9 @@ public class AlignmentUtils
         }
         else
         {
-          gapsToAdd = Math.min(intronLength + trailingGapLength
-                  - sourceGapMappedLength, trailingGapLength);
+          gapsToAdd = Math.min(
+                  intronLength + trailingGapLength - sourceGapMappedLength,
+                  trailingGapLength);
         }
       }
     }
@@ -857,7 +886,7 @@ public class AlignmentUtils
       System.err.println("Wrong alignment type in alignProteinAsDna");
       return 0;
     }
-    List<SequenceI> unmappedProtein = new ArrayList<SequenceI>();
+    List<SequenceI> unmappedProtein = new ArrayList<>();
     Map<AlignedCodon, Map<SequenceI, AlignedCodon>> alignedCodons = buildCodonColumnsMap(
             protein, dna, unmappedProtein);
     return alignProteinAs(protein, alignedCodons, unmappedProtein);
@@ -867,6 +896,8 @@ public class AlignmentUtils
    * Realigns the given dna to match the alignment of the protein, using codon
    * mappings to translate aligned peptide positions to codons.
    * 
+   * Always produces a padded CDS alignment.
+   * 
    * @param dna
    *          the alignment whose sequences are realigned by this method
    * @param protein
@@ -883,6 +914,7 @@ public class AlignmentUtils
     // todo: implement this
     List<AlignedCodonFrame> mappings = protein.getCodonFrames();
     int alignedCount = 0;
+    int width = 0; // alignment width for padding CDS
     for (SequenceI dnaSeq : dna.getSequences())
     {
       if (alignCdsSequenceAsProtein(dnaSeq, protein, mappings,
@@ -890,6 +922,18 @@ public class AlignmentUtils
       {
         alignedCount++;
       }
+      width = Math.max(dnaSeq.getLength(), width);
+    }
+    int oldwidth;
+    int diff;
+    for (SequenceI dnaSeq : dna.getSequences())
+    {
+      oldwidth = dnaSeq.getLength();
+      diff = width - oldwidth;
+      if (diff > 0)
+      {
+        dnaSeq.insertCharAt(oldwidth, diff, dna.getGapCharacter());
+      }
     }
     return alignedCount;
   }
@@ -906,7 +950,8 @@ public class AlignmentUtils
    * @return
    */
   static boolean alignCdsSequenceAsProtein(SequenceI cdsSeq,
-          AlignmentI protein, List<AlignedCodonFrame> mappings, char gapChar)
+          AlignmentI protein, List<AlignedCodonFrame> mappings,
+          char gapChar)
   {
     SequenceI cdsDss = cdsSeq.getDatasetSequence();
     if (cdsDss == null)
@@ -915,15 +960,15 @@ public class AlignmentUtils
               .println("alignCdsSequenceAsProtein needs aligned sequence!");
       return false;
     }
-    
+
     List<AlignedCodonFrame> dnaMappings = MappingUtils
             .findMappingsForSequence(cdsSeq, mappings);
     for (AlignedCodonFrame mapping : dnaMappings)
     {
       SequenceI peptide = mapping.findAlignedSequence(cdsSeq, protein);
-      int peptideLength = peptide.getLength();
       if (peptide != null)
       {
+        final int peptideLength = peptide.getLength();
         Mapping map = mapping.getMappingBetween(cdsSeq, peptide);
         if (map != null)
         {
@@ -932,44 +977,45 @@ public class AlignmentUtils
           {
             mapList = mapList.getInverse();
           }
-          int cdsLength = cdsDss.getLength();
+          final int cdsLength = cdsDss.getLength();
           int mappedFromLength = MappingUtils.getLength(mapList
                   .getFromRanges());
           int mappedToLength = MappingUtils
                   .getLength(mapList.getToRanges());
-          boolean addStopCodon = (cdsLength == mappedFromLength * 3 + 3)
-                  || (peptide.getDatasetSequence().getLength() == mappedFromLength - 1);
+          boolean addStopCodon = (cdsLength == mappedFromLength
+                  * CODON_LENGTH + CODON_LENGTH)
+                  || (peptide.getDatasetSequence()
+                          .getLength() == mappedFromLength - 1);
           if (cdsLength != mappedToLength && !addStopCodon)
           {
-            System.err
-                    .println(String
-                            .format("Can't align cds as protein (length mismatch %d/%d): %s",
-                                    cdsLength, mappedToLength,
-                                    cdsSeq.getName()));
+            System.err.println(String.format(
+                    "Can't align cds as protein (length mismatch %d/%d): %s",
+                    cdsLength, mappedToLength, cdsSeq.getName()));
           }
 
           /*
            * pre-fill the aligned cds sequence with gaps
            */
-          char[] alignedCds = new char[peptideLength * 3
-                  + (addStopCodon ? 3 : 0)];
+          char[] alignedCds = new char[peptideLength * CODON_LENGTH
+                  + (addStopCodon ? CODON_LENGTH : 0)];
           Arrays.fill(alignedCds, gapChar);
 
           /*
            * walk over the aligned peptide sequence and insert mapped 
            * codons for residues in the aligned cds sequence 
            */
-          char[] alignedPeptide = peptide.getSequence();
-          char[] nucleotides = cdsDss.getSequence();
           int copiedBases = 0;
           int cdsStart = cdsDss.getStart();
           int proteinPos = peptide.getStart() - 1;
           int cdsCol = 0;
-          for (char residue : alignedPeptide)
+
+          for (int col = 0; col < peptideLength; col++)
           {
+            char residue = peptide.getCharAt(col);
+
             if (Comparison.isGap(residue))
             {
-              cdsCol += 3;
+              cdsCol += CODON_LENGTH;
             }
             else
             {
@@ -978,13 +1024,13 @@ public class AlignmentUtils
               if (codon == null)
               {
                 // e.g. incomplete start codon, X in peptide
-                cdsCol += 3;
+                cdsCol += CODON_LENGTH;
               }
               else
               {
                 for (int j = codon[0]; j <= codon[1]; j++)
                 {
-                  char mappedBase = nucleotides[j - cdsStart];
+                  char mappedBase = cdsDss.getCharAt(j - cdsStart);
                   alignedCds[cdsCol++] = mappedBase;
                   copiedBases++;
                 }
@@ -996,7 +1042,7 @@ public class AlignmentUtils
            * append stop codon if not mapped from protein,
            * closing it up to the end of the mapped sequence
            */
-          if (copiedBases == nucleotides.length - 3)
+          if (copiedBases == cdsLength - CODON_LENGTH)
           {
             for (int i = alignedCds.length - 1; i >= 0; i--)
             {
@@ -1006,9 +1052,9 @@ public class AlignmentUtils
                 break;
               }
             }
-            for (int i = nucleotides.length - 3; i < nucleotides.length; i++)
+            for (int i = cdsLength - CODON_LENGTH; i < cdsLength; i++)
             {
-              alignedCds[cdsCol++] = nucleotides[i];
+              alignedCds[cdsCol++] = cdsDss.getCharAt(i);
             }
           }
           cdsSeq.setSequence(new String(alignedCds));
@@ -1051,7 +1097,7 @@ public class AlignmentUtils
      * {dnaSequence, {proteinSequence, codonProduct}} at that position. The
      * comparator keeps the codon positions ordered.
      */
-    Map<AlignedCodon, Map<SequenceI, AlignedCodon>> alignedCodons = new TreeMap<AlignedCodon, Map<SequenceI, AlignedCodon>>(
+    Map<AlignedCodon, Map<SequenceI, AlignedCodon>> alignedCodons = new TreeMap<>(
             new CodonComparator());
 
     for (SequenceI dnaSeq : dna.getSequences())
@@ -1062,8 +1108,8 @@ public class AlignmentUtils
         if (prot != null)
         {
           Mapping seqMap = mapping.getMappingForSequence(dnaSeq);
-          addCodonPositions(dnaSeq, prot, protein.getGapCharacter(),
-                  seqMap, alignedCodons);
+          addCodonPositions(dnaSeq, prot, protein.getGapCharacter(), seqMap,
+                  alignedCodons);
           unmappedProtein.remove(prot);
         }
       }
@@ -1076,7 +1122,7 @@ public class AlignmentUtils
     // TODO resolve JAL-2022 so this fudge can be removed
     int mappedSequenceCount = protein.getHeight() - unmappedProtein.size();
     addUnmappedPeptideStarts(alignedCodons, mappedSequenceCount);
-    
+
     return alignedCodons;
   }
 
@@ -1097,9 +1143,9 @@ public class AlignmentUtils
     // TODO delete this ugly hack once JAL-2022 is resolved
     // i.e. we can model startPhase > 0 (incomplete start codon)
 
-    List<SequenceI> sequencesChecked = new ArrayList<SequenceI>();
+    List<SequenceI> sequencesChecked = new ArrayList<>();
     AlignedCodon lastCodon = null;
-    Map<SequenceI, AlignedCodon> toAdd = new HashMap<SequenceI, AlignedCodon>();
+    Map<SequenceI, AlignedCodon> toAdd = new HashMap<>();
 
     for (Entry<AlignedCodon, Map<SequenceI, AlignedCodon>> entry : alignedCodons
             .entrySet())
@@ -1116,8 +1162,8 @@ public class AlignmentUtils
         AlignedCodon codon = sequenceCodon.getValue();
         if (codon.peptideCol > 1)
         {
-          System.err
-                  .println("Problem mapping protein with >1 unmapped start positions: "
+          System.err.println(
+                  "Problem mapping protein with >1 unmapped start positions: "
                           + seq.getName());
         }
         else if (codon.peptideCol == 1)
@@ -1128,8 +1174,8 @@ public class AlignmentUtils
           if (lastCodon != null)
           {
             AlignedCodon firstPeptide = new AlignedCodon(lastCodon.pos1,
-                    lastCodon.pos2, lastCodon.pos3, String.valueOf(seq
-                            .getCharAt(0)), 0);
+                    lastCodon.pos2, lastCodon.pos3,
+                    String.valueOf(seq.getCharAt(0)), 0);
             toAdd.put(seq, firstPeptide);
           }
           else
@@ -1178,21 +1224,26 @@ public class AlignmentUtils
           List<SequenceI> unmappedProtein)
   {
     /*
-     * Prefill aligned sequences with gaps before inserting aligned protein
-     * residues.
+     * prefill peptide sequences with gaps 
      */
     int alignedWidth = alignedCodons.size();
     char[] gaps = new char[alignedWidth];
     Arrays.fill(gaps, protein.getGapCharacter());
-    String allGaps = String.valueOf(gaps);
+    Map<SequenceI, char[]> peptides = new HashMap<>();
     for (SequenceI seq : protein.getSequences())
     {
       if (!unmappedProtein.contains(seq))
       {
-        seq.setSequence(allGaps);
+        peptides.put(seq, Arrays.copyOf(gaps, gaps.length));
       }
     }
 
+    /*
+     * Traverse the codons left to right (as defined by CodonComparator)
+     * and insert peptides in each column where the sequence is mapped.
+     * This gives a peptide 'alignment' where residues are aligned if their
+     * corresponding codons occupy the same columns in the cdna alignment.
+     */
     int column = 0;
     for (AlignedCodon codon : alignedCodons.keySet())
     {
@@ -1200,12 +1251,20 @@ public class AlignmentUtils
               .get(codon);
       for (Entry<SequenceI, AlignedCodon> entry : columnResidues.entrySet())
       {
-        // place translated codon at its column position in sequence
-        entry.getKey().getSequence()[column] = entry.getValue().product
-                .charAt(0);
+        char residue = entry.getValue().product.charAt(0);
+        peptides.get(entry.getKey())[column] = residue;
       }
       column++;
     }
+
+    /*
+     * and finally set the constructed sequences
+     */
+    for (Entry<SequenceI, char[]> entry : peptides.entrySet())
+    {
+      entry.getKey().setSequence(new String(entry.getValue()));
+    }
+
     return 0;
   }
 
@@ -1265,7 +1324,7 @@ public class AlignmentUtils
     Map<SequenceI, AlignedCodon> seqProduct = alignedCodons.get(codon);
     if (seqProduct == null)
     {
-      seqProduct = new HashMap<SequenceI, AlignedCodon>();
+      seqProduct = new HashMap<>();
       alignedCodons.put(codon, seqProduct);
     }
     seqProduct.put(protein, codon);
@@ -1278,7 +1337,8 @@ public class AlignmentUtils
    * <ul>
    * <li>One alignment must be nucleotide, and the other protein</li>
    * <li>At least one pair of sequences must be already mapped, or mappable</li>
-   * <li>Mappable means the nucleotide translation matches the protein sequence</li>
+   * <li>Mappable means the nucleotide translation matches the protein
+   * sequence</li>
    * <li>The translation may ignore start and stop codons if present in the
    * nucleotide</li>
    * </ul>
@@ -1334,9 +1394,10 @@ public class AlignmentUtils
       return false;
     }
 
-    SequenceI dnaDs = dnaSeq.getDatasetSequence() == null ? dnaSeq : dnaSeq
-            .getDatasetSequence();
-    SequenceI proteinDs = proteinSeq.getDatasetSequence() == null ? proteinSeq
+    SequenceI dnaDs = dnaSeq.getDatasetSequence() == null ? dnaSeq
+            : dnaSeq.getDatasetSequence();
+    SequenceI proteinDs = proteinSeq.getDatasetSequence() == null
+            ? proteinSeq
             : proteinSeq.getDatasetSequence();
 
     for (AlignedCodonFrame mapping : mappings)
@@ -1373,8 +1434,7 @@ public class AlignmentUtils
    *          the alignment to check for presence of annotations
    */
   public static void findAddableReferenceAnnotations(
-          List<SequenceI> sequenceScope,
-          Map<String, String> labelForCalcId,
+          List<SequenceI> sequenceScope, Map<String, String> labelForCalcId,
           final Map<SequenceI, List<AlignmentAnnotation>> candidates,
           AlignmentI al)
   {
@@ -1401,7 +1461,7 @@ public class AlignmentUtils
       {
         continue;
       }
-      final List<AlignmentAnnotation> result = new ArrayList<AlignmentAnnotation>();
+      final List<AlignmentAnnotation> result = new ArrayList<>();
       for (AlignmentAnnotation dsann : datasetAnnotations)
       {
         /*
@@ -1478,8 +1538,8 @@ public class AlignmentUtils
 
   /**
    * Set visibility of alignment annotations of specified types (labels), for
-   * specified sequences. This supports controls like
-   * "Show all secondary structure", "Hide all Temp factor", etc.
+   * specified sequences. This supports controls like "Show all secondary
+   * structure", "Hide all Temp factor", etc.
    * 
    * @al the alignment to scan for annotations
    * @param types
@@ -1503,9 +1563,8 @@ public class AlignmentUtils
       {
         if (anyType || types.contains(aa.label))
         {
-          if ((aa.sequenceRef != null)
-                  && (forSequences == null || forSequences
-                          .contains(aa.sequenceRef)))
+          if ((aa.sequenceRef != null) && (forSequences == null
+                  || forSequences.contains(aa.sequenceRef)))
           {
             aa.visible = doShow;
           }
@@ -1584,13 +1643,13 @@ public class AlignmentUtils
       throw new IllegalArgumentException(
               "IMPLEMENTATION ERROR: dataset.getDataset() must be null!");
     }
-    List<SequenceI> foundSeqs = new ArrayList<SequenceI>();
-    List<SequenceI> cdsSeqs = new ArrayList<SequenceI>();
+    List<SequenceI> foundSeqs = new ArrayList<>();
+    List<SequenceI> cdsSeqs = new ArrayList<>();
     List<AlignedCodonFrame> mappings = dataset.getCodonFrames();
     HashSet<SequenceI> productSeqs = null;
     if (products != null)
     {
-      productSeqs = new HashSet<SequenceI>();
+      productSeqs = new HashSet<>();
       for (SequenceI seq : products)
       {
         productSeqs.add(seq.getDatasetSequence() == null ? seq : seq
@@ -1667,11 +1726,20 @@ public class AlignmentUtils
            * didn't find mapped CDS sequence - construct it and add
            * its dataset sequence to the dataset
            */
-          cdsSeq = makeCdsSequence(dnaSeq.getDatasetSequence(), aMapping);
-          SequenceI cdsSeqDss = cdsSeq.createDatasetSequence();
+          cdsSeq = makeCdsSequence(dnaSeq.getDatasetSequence(), aMapping,
+                  dataset).deriveSequence();
+          // cdsSeq has a name constructed as CDS|<dbref>
+          // <dbref> will be either the accession for the coding sequence,
+          // marked in the /via/ dbref to the protein product accession
+          // or it will be the original nucleotide accession.
+          SequenceI cdsSeqDss = cdsSeq.getDatasetSequence();
+
           cdsSeqs.add(cdsSeq);
+
           if (!dataset.getSequences().contains(cdsSeqDss))
           {
+            // check if this sequence is a newly created one
+            // so needs adding to the dataset
             dataset.addSequence(cdsSeqDss);
           }
 
@@ -1680,10 +1748,12 @@ public class AlignmentUtils
            */
           List<int[]> cdsRange = Collections.singletonList(new int[] { 1,
               cdsSeq.getLength() });
-          MapList cdsToProteinMap = new MapList(cdsRange, mapList.getToRanges(),
-                  mapList.getFromRatio(), mapList.getToRatio());
+          MapList cdsToProteinMap = new MapList(cdsRange,
+                  mapList.getToRanges(), mapList.getFromRatio(),
+                  mapList.getToRatio());
           AlignedCodonFrame cdsToProteinMapping = new AlignedCodonFrame();
-          cdsToProteinMapping.addMap(cdsSeq, proteinProduct, cdsToProteinMap);
+          cdsToProteinMapping.addMap(cdsSeqDss, proteinProduct,
+                  cdsToProteinMap);
 
           /*
            * guard against duplicating the mapping if repeating this action
@@ -1693,31 +1763,15 @@ public class AlignmentUtils
             mappings.add(cdsToProteinMapping);
           }
 
-          /*
-           * copy protein's dbrefs to CDS sequence
-           * this enables Get Cross-References from CDS alignment
-           */
-          DBRefEntry[] proteinRefs = DBRefUtils.selectDbRefs(false,
-                  proteinProduct.getDBRefs());
-          if (proteinRefs != null)
-          {
-            for (DBRefEntry ref : proteinRefs)
-            {
-              DBRefEntry cdsToProteinRef = new DBRefEntry(ref);
-              cdsToProteinRef.setMap(new Mapping(proteinProduct,
-                      cdsToProteinMap));
-              cdsSeqDss.addDBRef(cdsToProteinRef);
-            }
-          }
-
+          propagateDBRefsToCDS(cdsSeqDss, dnaSeq.getDatasetSequence(),
+                  proteinProduct, aMapping);
           /*
            * add another mapping from original 'from' range to CDS
            */
           AlignedCodonFrame dnaToCdsMapping = new AlignedCodonFrame();
-          MapList dnaToCdsMap = new MapList(mapList.getFromRanges(),
-                  cdsRange, 1,
-                  1);
-          dnaToCdsMapping.addMap(dnaSeq.getDatasetSequence(), cdsSeq,
+          final MapList dnaToCdsMap = new MapList(mapList.getFromRanges(),
+                  cdsRange, 1, 1);
+          dnaToCdsMapping.addMap(dnaSeq.getDatasetSequence(), cdsSeqDss,
                   dnaToCdsMap);
           if (!mappings.contains(dnaToCdsMapping))
           {
@@ -1725,18 +1779,53 @@ public class AlignmentUtils
           }
 
           /*
+           * transfer dna chromosomal loci (if known) to the CDS
+           * sequence (via the mapping)
+           */
+          final MapList cdsToDnaMap = dnaToCdsMap.getInverse();
+          transferGeneLoci(dnaSeq, cdsToDnaMap, cdsSeq);
+
+          /*
            * add DBRef with mapping from protein to CDS
            * (this enables Get Cross-References from protein alignment)
            * This is tricky because we can't have two DBRefs with the
            * same source and accession, so need a different accession for
            * the CDS from the dna sequence
            */
-          DBRefEntryI dnaRef = dnaDss.getSourceDBRef();
-          if (dnaRef != null)
+
+          // specific use case:
+          // Genomic contig ENSCHR:1, contains coding regions for ENSG01,
+          // ENSG02, ENSG03, with transcripts and products similarly named.
+          // cannot add distinct dbrefs mapping location on ENSCHR:1 to ENSG01
+
+          // JBPNote: ?? can't actually create an example that demonstrates we
+          // need to
+          // synthesize an xref.
+
+          for (DBRefEntry primRef : dnaDss.getPrimaryDBRefs())
           {
+            /*
+             * create a cross-reference from CDS to the source sequence's
+             * primary reference and vice versa
+             */
+            String source = primRef.getSource();
+            String version = primRef.getVersion();
+            DBRefEntry cdsCrossRef = new DBRefEntry(source, source + ":"
+                    + version, primRef.getAccessionId());
+            cdsCrossRef.setMap(new Mapping(dnaDss, new MapList(cdsToDnaMap)));
+            cdsSeqDss.addDBRef(cdsCrossRef);
+
+            dnaSeq.addDBRef(new DBRefEntry(source, version, cdsSeq
+                    .getName(), new Mapping(cdsSeqDss, dnaToCdsMap)));
+
+            // problem here is that the cross-reference is synthesized -
+            // cdsSeq.getName() may be like 'CDS|dnaaccession' or
+            // 'CDS|emblcdsacc'
             // assuming cds version same as dna ?!?
-            DBRefEntry proteinToCdsRef = new DBRefEntry(dnaRef.getSource(),
-                    dnaRef.getVersion(), cdsSeq.getName());
+
+            DBRefEntry proteinToCdsRef = new DBRefEntry(source, version,
+                    cdsSeq.getName());
+            //
             proteinToCdsRef.setMap(new Mapping(cdsSeqDss, cdsToProteinMap
                     .getInverse()));
             proteinProduct.addDBRef(proteinToCdsRef);
@@ -1745,7 +1834,7 @@ public class AlignmentUtils
           /*
            * transfer any features on dna that overlap the CDS
            */
-          transferFeatures(dnaSeq, cdsSeq, cdsToProteinMap, null,
+          transferFeatures(dnaSeq, cdsSeq, dnaToCdsMap, null,
                   SequenceOntologyI.CDS);
         }
       }
@@ -1759,6 +1848,38 @@ public class AlignmentUtils
   }
 
   /**
+   * Tries to transfer gene loci (dbref to chromosome positions) from fromSeq to
+   * toSeq, mediated by the given mapping between the sequences
+   * 
+   * @param fromSeq
+   * @param targetToFrom
+   *          Map
+   * @param targetSeq
+   */
+  protected static void transferGeneLoci(SequenceI fromSeq,
+          MapList targetToFrom, SequenceI targetSeq)
+  {
+    if (targetSeq.getGeneLoci() != null)
+    {
+      // already have - don't override
+      return;
+    }
+    GeneLociI fromLoci = fromSeq.getGeneLoci();
+    if (fromLoci == null)
+    {
+      return;
+    }
+
+    MapList newMap = targetToFrom.traverse(fromLoci.getMapping());
+
+    if (newMap != null)
+    {
+      targetSeq.setGeneLoci(fromLoci.getSpeciesId(),
+              fromLoci.getAssemblyId(), fromLoci.getChromosomeId(), newMap);
+    }
+  }
+
+  /**
    * A helper method that finds a CDS sequence in the alignment dataset that is
    * mapped to the given protein sequence, and either is, or has a mapping from,
    * the given dna sequence.
@@ -1770,7 +1891,7 @@ public class AlignmentUtils
    * @param seqMappings
    *          the set of mappings involving dnaSeq
    * @param aMapping
-   *          an initial candidate from seqMappings
+   *          a transcript-to-peptide mapping
    * @return
    */
   static SequenceI findCdsForProtein(List<AlignedCodonFrame> mappings,
@@ -1789,12 +1910,21 @@ public class AlignmentUtils
      * is this mapping from the whole dna sequence (i.e. CDS)?
      * allowing for possible stop codon on dna but not peptide
      */
-    int mappedFromLength = MappingUtils.getLength(aMapping.getMap()
-            .getFromRanges());
+    int mappedFromLength = MappingUtils
+            .getLength(aMapping.getMap().getFromRanges());
     int dnaLength = seqDss.getLength();
-    if (mappedFromLength == dnaLength || mappedFromLength == dnaLength - 3)
+    if (mappedFromLength == dnaLength
+            || mappedFromLength == dnaLength - CODON_LENGTH)
     {
-      return seqDss;
+      /*
+       * if sequence has CDS features, this is a transcript with no UTR
+       * - do not take this as the CDS sequence! (JAL-2789)
+       */
+      if (seqDss.getFeatures().getFeaturesByOntology(SequenceOntologyI.CDS)
+              .isEmpty())
+      {
+        return seqDss;
+      }
     }
 
     /*
@@ -1808,20 +1938,23 @@ public class AlignmentUtils
       for (SequenceToSequenceMapping map : acf.getMappings())
       {
         Mapping mapping = map.getMapping();
-        if (mapping != aMapping && mapping.getMap().getFromRatio() == 3
+        if (mapping != aMapping
+                && mapping.getMap().getFromRatio() == CODON_LENGTH
                 && proteinProduct == mapping.getTo()
                 && seqDss != map.getFromSeq())
         {
-          mappedFromLength = MappingUtils.getLength(mapping.getMap()
-                  .getFromRanges());
+          mappedFromLength = MappingUtils
+                  .getLength(mapping.getMap().getFromRanges());
           if (mappedFromLength == map.getFromSeq().getLength())
           {
             /*
             * found a 3:1 mapping to the protein product which covers
-            * the whole dna sequence i.e. is from CDS; finally check it
-            * is from the dna start sequence
+            * the whole dna sequence i.e. is from CDS; finally check the CDS
+            * is mapped from the given dna start sequence
             */
             SequenceI cdsSeq = map.getFromSeq();
+            // todo this test is weak if seqMappings contains multiple mappings;
+            // we get away with it if transcript:cds relationship is 1:1
             List<AlignedCodonFrame> dnaToCdsMaps = MappingUtils
                     .findMappingsForSequence(cdsSeq, seqMappings);
             if (!dnaToCdsMaps.isEmpty())
@@ -1842,9 +1975,14 @@ public class AlignmentUtils
    * 
    * @param seq
    * @param mapping
+   * @param dataset
+   *          - existing dataset. We check for sequences that look like the CDS
+   *          we are about to construct, if one exists already, then we will
+   *          just return that one.
    * @return CDS sequence (as a dataset sequence)
    */
-  static SequenceI makeCdsSequence(SequenceI seq, Mapping mapping)
+  static SequenceI makeCdsSequence(SequenceI seq, Mapping mapping,
+          AlignmentI dataset)
   {
     char[] seqChars = seq.getSequence();
     List<int[]> fromRanges = mapping.getMap().getFromRanges();
@@ -1879,26 +2017,141 @@ public class AlignmentUtils
     String mapFromId = mapping.getMappedFromId();
     String seqId = "CDS|" + (mapFromId != null ? mapFromId : seq.getName());
     SequenceI newSeq = new Sequence(seqId, newSeqChars, 1, newPos);
+    if (dataset != null)
+    {
+      SequenceI[] matches = dataset.findSequenceMatch(newSeq.getName());
+      if (matches != null)
+      {
+        boolean matched = false;
+        for (SequenceI mtch : matches)
+        {
+          if (mtch.getStart() != newSeq.getStart())
+          {
+            continue;
+          }
+          if (mtch.getEnd() != newSeq.getEnd())
+          {
+            continue;
+          }
+          if (!Arrays.equals(mtch.getSequence(), newSeq.getSequence()))
+          {
+            continue;
+          }
+          if (!matched)
+          {
+            matched = true;
+            newSeq = mtch;
+          }
+          else
+          {
+            System.err.println(
+                    "JAL-2154 regression: warning - found (and ignnored a duplicate CDS sequence):"
+                            + mtch.toString());
+          }
+        }
+      }
+    }
     // newSeq.setDescription(mapFromId);
 
     return newSeq;
   }
 
   /**
+   * Adds any DBRefEntrys to cdsSeq from contig that have a Mapping congruent to
+   * the given mapping.
+   * 
+   * @param cdsSeq
+   * @param contig
+   * @param proteinProduct
+   * @param mapping
+   * @return list of DBRefEntrys added
+   */
+  protected static List<DBRefEntry> propagateDBRefsToCDS(SequenceI cdsSeq,
+          SequenceI contig, SequenceI proteinProduct, Mapping mapping)
+  {
+
+    // gather direct refs from contig congruent with mapping
+    List<DBRefEntry> direct = new ArrayList<>();
+    HashSet<String> directSources = new HashSet<>();
+
+    if (contig.getDBRefs() != null)
+    {
+      for (DBRefEntry dbr : contig.getDBRefs())
+      {
+        if (dbr.hasMap() && dbr.getMap().getMap().isTripletMap())
+        {
+          MapList map = dbr.getMap().getMap();
+          // check if map is the CDS mapping
+          if (mapping.getMap().equals(map))
+          {
+            direct.add(dbr);
+            directSources.add(dbr.getSource());
+          }
+        }
+      }
+    }
+    DBRefEntry[] onSource = DBRefUtils.selectRefs(
+            proteinProduct.getDBRefs(),
+            directSources.toArray(new String[0]));
+    List<DBRefEntry> propagated = new ArrayList<>();
+
+    // and generate appropriate mappings
+    for (DBRefEntry cdsref : direct)
+    {
+      // clone maplist and mapping
+      MapList cdsposmap = new MapList(
+              Arrays.asList(new int[][]
+              { new int[] { cdsSeq.getStart(), cdsSeq.getEnd() } }),
+              cdsref.getMap().getMap().getToRanges(), 3, 1);
+      Mapping cdsmap = new Mapping(cdsref.getMap().getTo(),
+              cdsref.getMap().getMap());
+
+      // create dbref
+      DBRefEntry newref = new DBRefEntry(cdsref.getSource(),
+              cdsref.getVersion(), cdsref.getAccessionId(),
+              new Mapping(cdsmap.getTo(), cdsposmap));
+
+      // and see if we can map to the protein product for this mapping.
+      // onSource is the filtered set of accessions on protein that we are
+      // tranferring, so we assume accession is the same.
+      if (cdsmap.getTo() == null && onSource != null)
+      {
+        List<DBRefEntry> sourceRefs = DBRefUtils.searchRefs(onSource,
+                cdsref.getAccessionId());
+        if (sourceRefs != null)
+        {
+          for (DBRefEntry srcref : sourceRefs)
+          {
+            if (srcref.getSource().equalsIgnoreCase(cdsref.getSource()))
+            {
+              // we have found a complementary dbref on the protein product, so
+              // update mapping's getTo
+              newref.getMap().setTo(proteinProduct);
+            }
+          }
+        }
+      }
+      cdsSeq.addDBRef(newref);
+      propagated.add(newref);
+    }
+    return propagated;
+  }
+
+  /**
    * Transfers co-located features on 'fromSeq' to 'toSeq', adjusting the
    * feature start/end ranges, optionally omitting specified feature types.
    * Returns the number of features copied.
    * 
    * @param fromSeq
    * @param toSeq
+   * @param mapping
+   *          the mapping from 'fromSeq' to 'toSeq'
    * @param select
    *          if not null, only features of this type are copied (including
    *          subtypes in the Sequence Ontology)
-   * @param mapping
-   *          the mapping from 'fromSeq' to 'toSeq'
    * @param omitting
    */
-  public static int transferFeatures(SequenceI fromSeq, SequenceI toSeq,
+  protected static int transferFeatures(SequenceI fromSeq, SequenceI toSeq,
           MapList mapping, String select, String... omitting)
   {
     SequenceI copyTo = toSeq;
@@ -1907,82 +2160,84 @@ public class AlignmentUtils
       copyTo = copyTo.getDatasetSequence();
     }
 
-    SequenceOntologyI so = SequenceOntologyFactory.getInstance();
+    /*
+     * get features, optionally restricted by an ontology term
+     */
+    List<SequenceFeature> sfs = select == null ? fromSeq.getFeatures()
+            .getPositionalFeatures() : fromSeq.getFeatures()
+            .getFeaturesByOntology(select);
+
     int count = 0;
-    SequenceFeature[] sfs = fromSeq.getSequenceFeatures();
-    if (sfs != null)
+    for (SequenceFeature sf : sfs)
     {
-      for (SequenceFeature sf : sfs)
+      String type = sf.getType();
+      boolean omit = false;
+      for (String toOmit : omitting)
       {
-        String type = sf.getType();
-        if (select != null && !so.isA(type, select))
+        if (type.equals(toOmit))
         {
-          continue;
-        }
-        boolean omit = false;
-        for (String toOmit : omitting)
-        {
-          if (type.equals(toOmit))
-          {
-            omit = true;
-          }
-        }
-        if (omit)
-        {
-          continue;
+          omit = true;
         }
+      }
+      if (omit)
+      {
+        continue;
+      }
 
-        /*
-         * locate the mapped range - null if either start or end is
-         * not mapped (no partial overlaps are calculated)
-         */
-        int start = sf.getBegin();
-        int end = sf.getEnd();
-        int[] mappedTo = mapping.locateInTo(start, end);
-        /*
-         * if whole exon range doesn't map, try interpreting it
-         * as 5' or 3' exon overlapping the CDS range
-         */
-        if (mappedTo == null)
-        {
-          mappedTo = mapping.locateInTo(end, end);
-          if (mappedTo != null)
-          {
-            /*
-             * end of exon is in CDS range - 5' overlap
-             * to a range from the start of the peptide
-             */
-            mappedTo[0] = 1;
-          }
-        }
-        if (mappedTo == null)
+      /*
+       * locate the mapped range - null if either start or end is
+       * not mapped (no partial overlaps are calculated)
+       */
+      int start = sf.getBegin();
+      int end = sf.getEnd();
+      int[] mappedTo = mapping.locateInTo(start, end);
+      /*
+       * if whole exon range doesn't map, try interpreting it
+       * as 5' or 3' exon overlapping the CDS range
+       */
+      if (mappedTo == null)
+      {
+        mappedTo = mapping.locateInTo(end, end);
+        if (mappedTo != null)
         {
-          mappedTo = mapping.locateInTo(start, start);
-          if (mappedTo != null)
-          {
-            /*
-             * start of exon is in CDS range - 3' overlap
-             * to a range up to the end of the peptide
-             */
-            mappedTo[1] = toSeq.getLength();
-          }
+          /*
+           * end of exon is in CDS range - 5' overlap
+           * to a range from the start of the peptide
+           */
+          mappedTo[0] = 1;
         }
+      }
+      if (mappedTo == null)
+      {
+        mappedTo = mapping.locateInTo(start, start);
         if (mappedTo != null)
         {
-          SequenceFeature copy = new SequenceFeature(sf);
-          copy.setBegin(Math.min(mappedTo[0], mappedTo[1]));
-          copy.setEnd(Math.max(mappedTo[0], mappedTo[1]));
-          copyTo.addSequenceFeature(copy);
-          count++;
+          /*
+           * start of exon is in CDS range - 3' overlap
+           * to a range up to the end of the peptide
+           */
+          mappedTo[1] = toSeq.getLength();
         }
       }
+      if (mappedTo != null)
+      {
+        int newBegin = Math.min(mappedTo[0], mappedTo[1]);
+        int newEnd = Math.max(mappedTo[0], mappedTo[1]);
+        SequenceFeature copy = new SequenceFeature(sf, newBegin, newEnd,
+                sf.getFeatureGroup(), sf.getScore());
+        copyTo.addSequenceFeature(copy);
+        count++;
+      }
     }
     return count;
   }
 
   /**
    * Returns a mapping from dna to protein by inspecting sequence features of
-   * type "CDS" on the dna.
+   * type "CDS" on the dna. A mapping is constructed if the total CDS feature
+   * length is 3 times the peptide length (optionally after dropping a trailing
+   * stop codon). This method does not check whether the CDS nucleotide sequence
+   * translates to the peptide sequence.
    * 
    * @param dnaSeq
    * @param proteinSeq
@@ -1994,6 +2249,16 @@ public class AlignmentUtils
     List<int[]> ranges = findCdsPositions(dnaSeq);
     int mappedDnaLength = MappingUtils.getLength(ranges);
 
+    /*
+     * if not a whole number of codons, truncate mapping
+     */
+    int codonRemainder = mappedDnaLength % CODON_LENGTH;
+    if (codonRemainder > 0)
+    {
+      mappedDnaLength -= codonRemainder;
+      MappingUtils.removeEndPositions(codonRemainder, ranges);
+    }
+
     int proteinLength = proteinSeq.getLength();
     int proteinStart = proteinSeq.getStart();
     int proteinEnd = proteinSeq.getEnd();
@@ -2008,28 +2273,32 @@ public class AlignmentUtils
       proteinStart++;
       proteinLength--;
     }
-    List<int[]> proteinRange = new ArrayList<int[]>();
+    List<int[]> proteinRange = new ArrayList<>();
 
     /*
      * dna length should map to protein (or protein plus stop codon)
      */
-    int codesForResidues = mappedDnaLength / 3;
+    int codesForResidues = mappedDnaLength / CODON_LENGTH;
     if (codesForResidues == (proteinLength + 1))
     {
       // assuming extra codon is for STOP and not in peptide
+      // todo: check trailing codon is indeed a STOP codon
       codesForResidues--;
+      mappedDnaLength -= CODON_LENGTH;
+      MappingUtils.removeEndPositions(CODON_LENGTH, ranges);
     }
+
     if (codesForResidues == proteinLength)
     {
       proteinRange.add(new int[] { proteinStart, proteinEnd });
-      return new MapList(ranges, proteinRange, 3, 1);
+      return new MapList(ranges, proteinRange, CODON_LENGTH, 1);
     }
     return null;
   }
 
   /**
    * Returns a list of CDS ranges found (as sequence positions base 1), i.e. of
-   * start/end positions of sequence features of type "CDS" (or a sub-type of
+   * [start, end] positions of sequence features of type "CDS" (or a sub-type of
    * CDS in the Sequence Ontology). The ranges are sorted into ascending start
    * position order, so this method is only valid for linear CDS in the same
    * sense as the protein product.
@@ -2037,62 +2306,46 @@ public class AlignmentUtils
    * @param dnaSeq
    * @return
    */
-  public static List<int[]> findCdsPositions(SequenceI dnaSeq)
+  protected static List<int[]> findCdsPositions(SequenceI dnaSeq)
   {
-    List<int[]> result = new ArrayList<int[]>();
-    SequenceFeature[] sfs = dnaSeq.getSequenceFeatures();
-    if (sfs == null)
+    List<int[]> result = new ArrayList<>();
+
+    List<SequenceFeature> sfs = dnaSeq.getFeatures().getFeaturesByOntology(
+            SequenceOntologyI.CDS);
+    if (sfs.isEmpty())
     {
       return result;
     }
-
-    SequenceOntologyI so = SequenceOntologyFactory.getInstance();
-    int startPhase = 0;
+    SequenceFeatures.sortFeatures(sfs, true);
 
     for (SequenceFeature sf : sfs)
     {
+      int phase = 0;
+      try
+      {
+        phase = Integer.parseInt(sf.getPhase());
+      } catch (NumberFormatException e)
+      {
+        // ignore
+      }
       /*
-       * process a CDS feature (or a sub-type of CDS)
+       * phase > 0 on first codon means 5' incomplete - skip to the start
+       * of the next codon; example ENST00000496384
        */
-      if (so.isA(sf.getType(), SequenceOntologyI.CDS))
+      int begin = sf.getBegin();
+      int end = sf.getEnd();
+      if (result.isEmpty() && phase > 0)
       {
-        int phase = 0;
-        try
-        {
-          phase = Integer.parseInt(sf.getPhase());
-        } catch (NumberFormatException e)
+        begin += phase;
+        if (begin > end)
         {
-          // ignore
-        }
-        /*
-         * phase > 0 on first codon means 5' incomplete - skip to the start
-         * of the next codon; example ENST00000496384
-         */
-        int begin = sf.getBegin();
-        int end = sf.getEnd();
-        if (result.isEmpty())
-        {
-          begin += phase;
-          if (begin > end)
-          {
-            // shouldn't happen!
-            System.err
-                    .println("Error: start phase extends beyond start CDS in "
-                            + dnaSeq.getName());
-          }
+          // shouldn't happen!
+          System.err
+                  .println("Error: start phase extends beyond start CDS in "
+                          + dnaSeq.getName());
         }
-        result.add(new int[] { begin, end });
       }
-    }
-
-    /*
-     * remove 'startPhase' positions (usually 0) from the first range 
-     * so we begin at the start of a complete codon
-     */
-    if (!result.isEmpty())
-    {
-      // TODO JAL-2022 correctly model start phase > 0
-      result.get(0)[0] += startPhase;
+      result.add(new int[] { begin, end });
     }
 
     /*
@@ -2102,14 +2355,7 @@ public class AlignmentUtils
      * ranges are assembled in order. Other cases should not use this method,
      * but instead construct an explicit mapping for CDS (e.g. EMBL parsing).
      */
-    Collections.sort(result, new Comparator<int[]>()
-    {
-      @Override
-      public int compare(int[] o1, int[] o2)
-      {
-        return Integer.compare(o1[0], o2[0]);
-      }
-    });
+    Collections.sort(result, IntRangeComparator.ASCENDING);
     return result;
   }
 
@@ -2162,24 +2408,6 @@ public class AlignmentUtils
       count += computePeptideVariants(peptide, peptidePos, codonVariants);
     }
 
-    /*
-     * sort to get sequence features in start position order
-     * - would be better to store in Sequence as a TreeSet or NCList?
-     */
-    if (peptide.getSequenceFeatures() != null)
-    {
-      Arrays.sort(peptide.getSequenceFeatures(),
-              new Comparator<SequenceFeature>()
-              {
-                @Override
-                public int compare(SequenceFeature o1, SequenceFeature o2)
-                {
-                  int c = Integer.compare(o1.getBegin(), o2.getBegin());
-                  return c == 0 ? Integer.compare(o1.getEnd(), o2.getEnd())
-                          : c;
-                }
-              });
-    }
     return count;
   }
 
@@ -2213,15 +2441,22 @@ public class AlignmentUtils
     {
       if (var.variant != null)
       {
-        String alleles = (String) var.variant.getValue("alleles");
+        String alleles = (String) var.variant.getValue(Gff3Helper.ALLELES);
         if (alleles != null)
         {
           for (String base : alleles.split(","))
           {
-            String codon = base + base2 + base3;
-            if (addPeptideVariant(peptide, peptidePos, residue, var, codon))
+            if (!base1.equalsIgnoreCase(base))
             {
-              count++;
+              String codon = base.toUpperCase() + base2.toLowerCase()
+                      + base3.toLowerCase();
+              String canonical = base1.toUpperCase() + base2.toLowerCase()
+                      + base3.toLowerCase();
+              if (addPeptideVariant(peptide, peptidePos, residue, var,
+                      codon, canonical))
+              {
+                count++;
+              }
             }
           }
         }
@@ -2235,15 +2470,22 @@ public class AlignmentUtils
     {
       if (var.variant != null)
       {
-        String alleles = (String) var.variant.getValue("alleles");
+        String alleles = (String) var.variant.getValue(Gff3Helper.ALLELES);
         if (alleles != null)
         {
           for (String base : alleles.split(","))
           {
-            String codon = base1 + base + base3;
-            if (addPeptideVariant(peptide, peptidePos, residue, var, codon))
+            if (!base2.equalsIgnoreCase(base))
             {
-              count++;
+              String codon = base1.toLowerCase() + base.toUpperCase()
+                      + base3.toLowerCase();
+              String canonical = base1.toLowerCase() + base2.toUpperCase()
+                      + base3.toLowerCase();
+              if (addPeptideVariant(peptide, peptidePos, residue, var,
+                      codon, canonical))
+              {
+                count++;
+              }
             }
           }
         }
@@ -2257,15 +2499,22 @@ public class AlignmentUtils
     {
       if (var.variant != null)
       {
-        String alleles = (String) var.variant.getValue("alleles");
+        String alleles = (String) var.variant.getValue(Gff3Helper.ALLELES);
         if (alleles != null)
         {
           for (String base : alleles.split(","))
           {
-            String codon = base1 + base2 + base;
-            if (addPeptideVariant(peptide, peptidePos, residue, var, codon))
+            if (!base3.equalsIgnoreCase(base))
             {
-              count++;
+              String codon = base1.toLowerCase() + base2.toLowerCase()
+                      + base.toUpperCase();
+              String canonical = base1.toLowerCase() + base2.toLowerCase()
+                      + base3.toUpperCase();
+              if (addPeptideVariant(peptide, peptidePos, residue, var,
+                      codon, canonical))
+              {
+                count++;
+              }
             }
           }
         }
@@ -2276,20 +2525,22 @@ public class AlignmentUtils
   }
 
   /**
-   * Helper method that adds a peptide variant feature, provided the given codon
-   * translates to a value different to the current residue (is a non-synonymous
-   * variant). ID and clinical_significance attributes of the dna variant (if
-   * present) are copied to the new feature.
+   * Helper method that adds a peptide variant feature. ID and
+   * clinical_significance attributes of the dna variant (if present) are copied
+   * to the new feature.
    * 
    * @param peptide
    * @param peptidePos
    * @param residue
    * @param var
    * @param codon
+   *          the variant codon e.g. aCg
+   * @param canonical
+   *          the 'normal' codon e.g. aTg
    * @return true if a feature was added, else false
    */
   static boolean addPeptideVariant(SequenceI peptide, int peptidePos,
-          String residue, DnaVariant var, String codon)
+          String residue, DnaVariant var, String codon, String canonical)
   {
     /*
      * get peptide translation of codon e.g. GAT -> D
@@ -2297,69 +2548,85 @@ public class AlignmentUtils
      * e.g. multibase variants or HGMD_MUTATION etc
      * are currently ignored here
      */
-    String trans = codon.contains("-") ? "-"
-            : (codon.length() > 3 ? null : ResidueProperties
-                    .codonTranslate(codon));
-    if (trans != null && !trans.equals(residue))
+    String trans = codon.contains("-") ? null
+            : (codon.length() > CODON_LENGTH ? null
+                    : ResidueProperties.codonTranslate(codon));
+    if (trans == null)
+    {
+      return false;
+    }
+    String desc = canonical + "/" + codon;
+    String featureType = "";
+    if (trans.equals(residue))
+    {
+      featureType = SequenceOntologyI.SYNONYMOUS_VARIANT;
+    }
+    else if (ResidueProperties.STOP.equals(trans))
+    {
+      featureType = SequenceOntologyI.STOP_GAINED;
+    }
+    else
     {
       String residue3Char = StringUtils
               .toSentenceCase(ResidueProperties.aa2Triplet.get(residue));
       String trans3Char = StringUtils
               .toSentenceCase(ResidueProperties.aa2Triplet.get(trans));
-      String desc = "p." + residue3Char + peptidePos + trans3Char;
-      // set score to 0f so 'graduated colour' option is offered! JAL-2060
-      SequenceFeature sf = new SequenceFeature(
-              SequenceOntologyI.SEQUENCE_VARIANT, desc, peptidePos,
-              peptidePos, 0f, "Jalview");
-      StringBuilder attributes = new StringBuilder(32);
-      String id = (String) var.variant.getValue(ID);
-      if (id != null)
-      {
-        if (id.startsWith(SEQUENCE_VARIANT))
-        {
-          id = id.substring(SEQUENCE_VARIANT.length());
-        }
-        sf.setValue(ID, id);
-        attributes.append(ID).append("=").append(id);
-        // TODO handle other species variants
-        StringBuilder link = new StringBuilder(32);
-        try
-        {
-          link.append(desc).append(" ").append(id)
-                  .append("|http://www.ensembl.org/Homo_sapiens/Variation/Summary?v=")
-                  .append(URLEncoder.encode(id, "UTF-8"));
-          sf.addLink(link.toString());
-        } catch (UnsupportedEncodingException e)
-        {
-          // as if
-        }
-      }
-      String clinSig = (String) var.variant
-              .getValue(CLINICAL_SIGNIFICANCE);
-      if (clinSig != null)
+      desc = "p." + residue3Char + peptidePos + trans3Char;
+      featureType = SequenceOntologyI.NONSYNONYMOUS_VARIANT;
+    }
+    SequenceFeature sf = new SequenceFeature(featureType, desc, peptidePos,
+            peptidePos, var.getSource());
+
+    StringBuilder attributes = new StringBuilder(32);
+    String id = (String) var.variant.getValue(VARIANT_ID);
+    if (id != null)
+    {
+      if (id.startsWith(SEQUENCE_VARIANT))
       {
-        sf.setValue(CLINICAL_SIGNIFICANCE, clinSig);
-        attributes.append(";").append(CLINICAL_SIGNIFICANCE).append("=")
-                .append(clinSig);
+        id = id.substring(SEQUENCE_VARIANT.length());
       }
-      peptide.addSequenceFeature(sf);
-      if (attributes.length() > 0)
+      sf.setValue(VARIANT_ID, id);
+      attributes.append(VARIANT_ID).append("=").append(id);
+      // TODO handle other species variants JAL-2064
+      StringBuilder link = new StringBuilder(32);
+      try
+      {
+        link.append(desc).append(" ").append(id).append(
+                "|http://www.ensembl.org/Homo_sapiens/Variation/Summary?v=")
+                .append(URLEncoder.encode(id, "UTF-8"));
+        sf.addLink(link.toString());
+      } catch (UnsupportedEncodingException e)
       {
-        sf.setAttributes(attributes.toString());
+        // as if
       }
-      return true;
     }
-    return false;
+    String clinSig = (String) var.variant.getValue(CLINICAL_SIGNIFICANCE);
+    if (clinSig != null)
+    {
+      sf.setValue(CLINICAL_SIGNIFICANCE, clinSig);
+      attributes.append(";").append(CLINICAL_SIGNIFICANCE).append("=")
+              .append(clinSig);
+    }
+    peptide.addSequenceFeature(sf);
+    if (attributes.length() > 0)
+    {
+      sf.setAttributes(attributes.toString());
+    }
+    return true;
   }
 
   /**
    * Builds a map whose key is position in the protein sequence, and value is a
-   * list of the base and all variants for each corresponding codon position
+   * list of the base and all variants for each corresponding codon position.
+   * <p>
+   * This depends on dna variants being held as a comma-separated list as
+   * property "alleles" on variant features.
    * 
    * @param dnaSeq
    * @param dnaToProtein
    * @return
    */
+  @SuppressWarnings("unchecked")
   static LinkedHashMap<Integer, List<DnaVariant>[]> buildDnaVariantsMap(
           SequenceI dnaSeq, MapList dnaToProtein)
   {
@@ -2367,11 +2634,11 @@ public class AlignmentUtils
      * map from peptide position to all variants of the codon which codes for it
      * LinkedHashMap ensures we keep the peptide features in sequence order
      */
-    LinkedHashMap<Integer, List<DnaVariant>[]> variants = new LinkedHashMap<Integer, List<DnaVariant>[]>();
-    SequenceOntologyI so = SequenceOntologyFactory.getInstance();
+    LinkedHashMap<Integer, List<DnaVariant>[]> variants = new LinkedHashMap<>();
 
-    SequenceFeature[] dnaFeatures = dnaSeq.getSequenceFeatures();
-    if (dnaFeatures == null)
+    List<SequenceFeature> dnaFeatures = dnaSeq.getFeatures()
+            .getFeaturesByOntology(SequenceOntologyI.SEQUENCE_VARIANT);
+    if (dnaFeatures.isEmpty())
     {
       return variants;
     }
@@ -2391,84 +2658,89 @@ public class AlignmentUtils
         // not handling multi-locus variant features
         continue;
       }
-      if (so.isA(sf.getType(), SequenceOntologyI.SEQUENCE_VARIANT))
+
+      /*
+       * ignore variant if not a SNP
+       */
+      String alls = (String) sf.getValue(Gff3Helper.ALLELES);
+      if (alls == null)
       {
-        int[] mapsTo = dnaToProtein.locateInTo(dnaCol, dnaCol);
-        if (mapsTo == null)
-        {
-          // feature doesn't lie within coding region
-          continue;
-        }
-        int peptidePosition = mapsTo[0];
-        List<DnaVariant>[] codonVariants = variants.get(peptidePosition);
-        if (codonVariants == null)
-        {
-          codonVariants = new ArrayList[3];
-          codonVariants[0] = new ArrayList<DnaVariant>();
-          codonVariants[1] = new ArrayList<DnaVariant>();
-          codonVariants[2] = new ArrayList<DnaVariant>();
-          variants.put(peptidePosition, codonVariants);
-        }
+        continue; // non-SNP VCF variant perhaps - can't process this
+      }
 
-        /*
-         * extract dna variants to a string array
-         */
-        String alls = (String) sf.getValue("alleles");
-        if (alls == null)
-        {
-          continue;
-        }
-        String[] alleles = alls.toUpperCase().split(",");
-        int i = 0;
-        for (String allele : alleles)
+      String[] alleles = alls.toUpperCase().split(",");
+      boolean isSnp = true;
+      for (String allele : alleles)
+      {
+        if (allele.trim().length() > 1)
         {
-          alleles[i++] = allele.trim(); // lose any space characters "A, G"
+          isSnp = false;
         }
+      }
+      if (!isSnp)
+      {
+        continue;
+      }
 
-        /*
-         * get this peptide's codon positions e.g. [3, 4, 5] or [4, 7, 10]
-         */
-        int[] codon = peptidePosition == lastPeptidePostion ? lastCodon
-                : MappingUtils.flattenRanges(dnaToProtein.locateInFrom(
-                        peptidePosition, peptidePosition));
-        lastPeptidePostion = peptidePosition;
-        lastCodon = codon;
+      int[] mapsTo = dnaToProtein.locateInTo(dnaCol, dnaCol);
+      if (mapsTo == null)
+      {
+        // feature doesn't lie within coding region
+        continue;
+      }
+      int peptidePosition = mapsTo[0];
+      List<DnaVariant>[] codonVariants = variants.get(peptidePosition);
+      if (codonVariants == null)
+      {
+        codonVariants = new ArrayList[CODON_LENGTH];
+        codonVariants[0] = new ArrayList<>();
+        codonVariants[1] = new ArrayList<>();
+        codonVariants[2] = new ArrayList<>();
+        variants.put(peptidePosition, codonVariants);
+      }
 
-        /*
-         * save nucleotide (and any variant) for each codon position
-         */
-        for (int codonPos = 0; codonPos < 3; codonPos++)
+      /*
+       * get this peptide's codon positions e.g. [3, 4, 5] or [4, 7, 10]
+       */
+      int[] codon = peptidePosition == lastPeptidePostion ? lastCodon
+              : MappingUtils.flattenRanges(dnaToProtein.locateInFrom(
+                      peptidePosition, peptidePosition));
+      lastPeptidePostion = peptidePosition;
+      lastCodon = codon;
+
+      /*
+       * save nucleotide (and any variant) for each codon position
+       */
+      for (int codonPos = 0; codonPos < CODON_LENGTH; codonPos++)
+      {
+        String nucleotide = String.valueOf(
+                dnaSeq.getCharAt(codon[codonPos] - dnaStart)).toUpperCase();
+        List<DnaVariant> codonVariant = codonVariants[codonPos];
+        if (codon[codonPos] == dnaCol)
         {
-          String nucleotide = String.valueOf(
-                  dnaSeq.getCharAt(codon[codonPos] - dnaStart))
-                  .toUpperCase();
-          List<DnaVariant> codonVariant = codonVariants[codonPos];
-          if (codon[codonPos] == dnaCol)
+          if (!codonVariant.isEmpty()
+                  && codonVariant.get(0).variant == null)
           {
-            if (!codonVariant.isEmpty()
-                    && codonVariant.get(0).variant == null)
-            {
-              /*
-               * already recorded base value, add this variant
-               */
-              codonVariant.get(0).variant = sf;
-            }
-            else
-            {
-              /*
-               * add variant with base value
-               */
-              codonVariant.add(new DnaVariant(nucleotide, sf));
-            }
+            /*
+             * already recorded base value, add this variant
+             */
+            codonVariant.get(0).variant = sf;
           }
-          else if (codonVariant.isEmpty())
+          else
           {
             /*
-             * record (possibly non-varying) base value
+             * add variant with base value
              */
-            codonVariant.add(new DnaVariant(nucleotide));
+            codonVariant.add(new DnaVariant(nucleotide, sf));
           }
         }
+        else if (codonVariant.isEmpty())
+        {
+          /*
+           * record (possibly non-varying) base value
+           */
+          codonVariant.add(new DnaVariant(nucleotide));
+        }
       }
     }
     return variants;
@@ -2490,7 +2762,7 @@ public class AlignmentUtils
   {
     AlignmentI copy = new Alignment(new Alignment(seqs));
     copy.setDataset(dataset);
-
+    boolean isProtein = !copy.isNucleotide();
     SequenceIdMatcher matcher = new SequenceIdMatcher(seqs);
     if (xrefs != null)
     {
@@ -2501,7 +2773,8 @@ public class AlignmentUtils
         {
           for (DBRefEntry dbref : dbrefs)
           {
-            if (dbref.getMap() == null || dbref.getMap().getTo() == null)
+            if (dbref.getMap() == null || dbref.getMap().getTo() == null
+                    || dbref.getMap().getTo().isProtein() != isProtein)
             {
               continue;
             }
@@ -2546,12 +2819,13 @@ public class AlignmentUtils
     /*
      * fancy case - aligning via mappings between sequences
      */
-    List<SequenceI> unmapped = new ArrayList<SequenceI>();
+    List<SequenceI> unmapped = new ArrayList<>();
     Map<Integer, Map<SequenceI, Character>> columnMap = buildMappedColumnsMap(
             unaligned, aligned, unmapped);
     int width = columnMap.size();
     char gap = unaligned.getGapCharacter();
     int realignedCount = 0;
+    // TODO: verify this loop scales sensibly for very wide/high alignments
 
     for (SequenceI seq : unaligned.getSequences())
     {
@@ -2581,7 +2855,7 @@ public class AlignmentUtils
           }
           newCol++;
         }
-        
+
         /*
          * trim trailing gaps
          */
@@ -2605,7 +2879,10 @@ public class AlignmentUtils
    * true; else returns false
    * 
    * @param unaligned
+   *          - sequences to be aligned based on aligned
    * @param aligned
+   *          - 'guide' alignment containing sequences derived from same dataset
+   *          as unaligned
    * @return
    */
   static boolean alignAsSameSequences(AlignmentI unaligned,
@@ -2616,10 +2893,16 @@ public class AlignmentUtils
       return false; // should only pass alignments with datasets here
     }
 
-    Map<SequenceI, SequenceI> alignedDatasets = new HashMap<SequenceI, SequenceI>();
+    // map from dataset sequence to alignment sequence(s)
+    Map<SequenceI, List<SequenceI>> alignedDatasets = new HashMap<>();
     for (SequenceI seq : aligned.getSequences())
     {
-      alignedDatasets.put(seq.getDatasetSequence(), seq);
+      SequenceI ds = seq.getDatasetSequence();
+      if (alignedDatasets.get(ds) == null)
+      {
+        alignedDatasets.put(ds, new ArrayList<SequenceI>());
+      }
+      alignedDatasets.get(ds).add(seq);
     }
 
     /*
@@ -2635,15 +2918,22 @@ public class AlignmentUtils
     }
 
     /*
-     * second pass - copy aligned sequences
+     * second pass - copy aligned sequences;
+     * heuristic rule: pair off sequences in order for the case where 
+     * more than one shares the same dataset sequence 
      */
     for (SequenceI seq : unaligned.getSequences())
     {
-      SequenceI alignedSequence = alignedDatasets.get(seq
-              .getDatasetSequence());
+      List<SequenceI> alignedSequences = alignedDatasets
+              .get(seq.getDatasetSequence());
       // TODO: getSequenceAsString() will be deprecated in the future
       // TODO: need to leave to SequenceI implementor to update gaps
-      seq.setSequence(alignedSequence.getSequenceAsString());
+      seq.setSequence(alignedSequences.get(0).getSequenceAsString());
+      if (alignedSequences.size() > 0)
+      {
+        // pop off aligned sequences (except the last one)
+        alignedSequences.remove(0);
+      }
     }
 
     return true;
@@ -2658,15 +2948,16 @@ public class AlignmentUtils
    * @param unmapped
    * @return
    */
-  static Map<Integer, Map<SequenceI, Character>> buildMappedColumnsMap(
-          AlignmentI unaligned, AlignmentI aligned, List<SequenceI> unmapped)
+  static SortedMap<Integer, Map<SequenceI, Character>> buildMappedColumnsMap(
+          AlignmentI unaligned, AlignmentI aligned,
+          List<SequenceI> unmapped)
   {
     /*
      * Map will hold, for each aligned column position, a map of
      * {unalignedSequence, characterPerSequence} at that position.
      * TreeMap keeps the entries in ascending column order. 
      */
-    Map<Integer, Map<SequenceI, Character>> map = new TreeMap<Integer, Map<SequenceI, Character>>();
+    SortedMap<Integer, Map<SequenceI, Character>> map = new TreeMap<>();
 
     /*
      * record any sequences that have no mapping so can't be realigned
@@ -2694,7 +2985,8 @@ public class AlignmentUtils
   }
 
   /**
-   * Helper method that adds to a map the mapped column positions of a sequence. <br>
+   * Helper method that adds to a map the mapped column positions of a sequence.
+   * <br>
    * For example if aaTT-Tg-gAAA is mapped to TTTAAA then the map should record
    * that columns 3,4,6,10,11,12 map to characters T,T,T,A,A,A of the mapped to
    * sequence.
@@ -2723,13 +3015,11 @@ public class AlignmentUtils
      */
     if (seqMap.getTo() == fromSeq.getDatasetSequence())
     {
-      seqMap = new Mapping(seq.getDatasetSequence(), seqMap.getMap()
-              .getInverse());
+      seqMap = new Mapping(seq.getDatasetSequence(),
+              seqMap.getMap().getInverse());
     }
 
-    char[] fromChars = fromSeq.getSequence();
     int toStart = seq.getStart();
-    char[] toChars = seq.getSequence();
 
     /*
      * traverse [start, end, start, end...] ranges in fromSeq
@@ -2760,10 +3050,10 @@ public class AlignmentUtils
          * of the next character of the mapped-to sequence; stop when all
          * the characters of the range have been counted
          */
-        while (mappedCharPos <= range[1] && fromCol <= fromChars.length
+        while (mappedCharPos <= range[1] && fromCol <= fromSeq.getLength()
                 && fromCol >= 0)
         {
-          if (!Comparison.isGap(fromChars[fromCol - 1]))
+          if (!Comparison.isGap(fromSeq.getCharAt(fromCol - 1)))
           {
             /*
              * mapped from sequence has a character in this column
@@ -2772,10 +3062,10 @@ public class AlignmentUtils
             Map<SequenceI, Character> seqsMap = map.get(fromCol);
             if (seqsMap == null)
             {
-              seqsMap = new HashMap<SequenceI, Character>();
+              seqsMap = new HashMap<>();
               map.put(fromCol, seqsMap);
             }
-            seqsMap.put(seq, toChars[mappedCharPos - toStart]);
+            seqsMap.put(seq, seq.getCharAt(mappedCharPos - toStart));
             mappedCharPos++;
           }
           fromCol += (forward ? 1 : -1);