JAL-2089 patch broken merge to master for Release 2.10.0b1
[jalview.git] / src / jalview / analysis / AlignmentUtils.java
index 20fcf25..34fe221 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;
@@ -73,22 +72,26 @@ 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";
 
   /**
    * 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 +99,11 @@ public class AlignmentUtils
       base = nuc;
       variant = var;
     }
+
+    public String getSource()
+    {
+      return variant == null ? null : variant.getFeatureGroup();
+    }
   }
 
   /**
@@ -428,7 +436,7 @@ 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 +448,14 @@ public class AlignmentUtils
      */
     if (cdnaLength != mappedLength && cdnaLength > 2)
     {
-      String lastCodon = String.valueOf(cdnaSeqChars, cdnaLength - 3, 3)
-              .toUpperCase();
+      String lastCodon = String.valueOf(cdnaSeqChars,
+              cdnaLength - CODON_LENGTH, CODON_LENGTH).toUpperCase();
       for (String stop : ResidueProperties.STOP)
       {
         if (lastCodon.equals(stop))
         {
-          cdnaEnd -= 3;
-          cdnaLength -= 3;
+          cdnaEnd -= CODON_LENGTH;
+          cdnaLength -= CODON_LENGTH;
           break;
         }
       }
@@ -459,12 +467,12 @@ public class AlignmentUtils
     int startOffset = 0;
     if (cdnaLength != mappedLength
             && cdnaLength > 2
-            && String.valueOf(cdnaSeqChars, 0, 3).toUpperCase()
+            && 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))
@@ -473,7 +481,7 @@ 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);
+      { proteinStart, proteinEnd }, CODON_LENGTH, 1);
       return map;
     }
 
@@ -503,10 +511,9 @@ public class AlignmentUtils
 
     int aaPos = 0;
     int dnaPos = cdnaStart;
-    for (; dnaPos < cdnaSeqChars.length - 2
-            && aaPos < aaSeqChars.length; dnaPos += 3, aaPos++)
+    for (; dnaPos < cdnaSeqChars.length - 2 && 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);
 
       /*
@@ -542,9 +549,9 @@ public class AlignmentUtils
     {
       return true;
     }
-    if (dnaPos == cdnaSeqChars.length - 3)
+    if (dnaPos == cdnaSeqChars.length - CODON_LENGTH)
     {
-      String codon = String.valueOf(cdnaSeqChars, dnaPos, 3);
+      String codon = String.valueOf(cdnaSeqChars, dnaPos, CODON_LENGTH);
       if ("STOP".equals(ResidueProperties.codonTranslate(codon)))
       {
         return true;
@@ -867,6 +874,8 @@ 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 +892,7 @@ 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 +900,18 @@ 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;
   }
@@ -915,15 +937,15 @@ 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)
       {
+        int peptideLength = peptide.getLength();
         Mapping map = mapping.getMappingBetween(cdsSeq, peptide);
         if (map != null)
         {
@@ -937,7 +959,8 @@ public class AlignmentUtils
                   .getFromRanges());
           int mappedToLength = MappingUtils
                   .getLength(mapList.getToRanges());
-          boolean addStopCodon = (cdsLength == mappedFromLength * 3 + 3)
+          boolean addStopCodon = (cdsLength == mappedFromLength
+                  * CODON_LENGTH + CODON_LENGTH)
                   || (peptide.getDatasetSequence().getLength() == mappedFromLength - 1);
           if (cdsLength != mappedToLength && !addStopCodon)
           {
@@ -951,8 +974,8 @@ public class AlignmentUtils
           /*
            * 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);
 
           /*
@@ -969,7 +992,7 @@ public class AlignmentUtils
           {
             if (Comparison.isGap(residue))
             {
-              cdsCol += 3;
+              cdsCol += CODON_LENGTH;
             }
             else
             {
@@ -978,7 +1001,7 @@ public class AlignmentUtils
               if (codon == null)
               {
                 // e.g. incomplete start codon, X in peptide
-                cdsCol += 3;
+                cdsCol += CODON_LENGTH;
               }
               else
               {
@@ -996,7 +1019,7 @@ 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 == nucleotides.length - CODON_LENGTH)
           {
             for (int i = alignedCds.length - 1; i >= 0; i--)
             {
@@ -1006,7 +1029,7 @@ public class AlignmentUtils
                 break;
               }
             }
-            for (int i = nucleotides.length - 3; i < nucleotides.length; i++)
+            for (int i = nucleotides.length - CODON_LENGTH; i < nucleotides.length; i++)
             {
               alignedCds[cdsCol++] = nucleotides[i];
             }
@@ -1076,7 +1099,7 @@ public class AlignmentUtils
     // TODO resolve JAL-2022 so this fudge can be removed
     int mappedSequenceCount = protein.getHeight() - unmappedProtein.size();
     addUnmappedPeptideStarts(alignedCodons, mappedSequenceCount);
-    
+
     return alignedCodons;
   }
 
@@ -1667,11 +1690,20 @@ 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 +1712,12 @@ 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 +1727,15 @@ 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,
+                  cdsRange, 1, 1);
+          dnaToCdsMapping.addMap(dnaSeq.getDatasetSequence(), cdsSeqDss,
                   dnaToCdsMap);
           if (!mappings.contains(dnaToCdsMapping))
           {
@@ -1731,12 +1749,37 @@ public class AlignmentUtils
            * 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())
           {
+            // creates a complementary cross-reference to the source sequence's
+            // primary reference.
+
+            DBRefEntry cdsCrossRef = new DBRefEntry(primRef.getSource(),
+                    primRef.getSource() + ":" + primRef.getVersion(),
+                    primRef.getAccessionId());
+            cdsCrossRef
+                    .setMap(new Mapping(dnaDss, new MapList(dnaToCdsMap)));
+            cdsSeqDss.addDBRef(cdsCrossRef);
+
+            // 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(
+                    primRef.getSource(), primRef.getVersion(),
+                    cdsSeq.getName());
+            //
             proteinToCdsRef.setMap(new Mapping(cdsSeqDss, cdsToProteinMap
                     .getInverse()));
             proteinProduct.addDBRef(proteinToCdsRef);
@@ -1745,7 +1788,7 @@ public class AlignmentUtils
           /*
            * transfer any features on dna that overlap the CDS
            */
-          transferFeatures(dnaSeq, cdsSeq, cdsToProteinMap, null,
+          transferFeatures(dnaSeq, cdsSeq, dnaToCdsMap, null,
                   SequenceOntologyI.CDS);
         }
       }
@@ -1792,7 +1835,8 @@ public class AlignmentUtils
     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;
     }
@@ -1808,7 +1852,8 @@ 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())
         {
@@ -1842,9 +1887,14 @@ 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();
@@ -1879,12 +1929,124 @@ 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;
   }
 
   /**
+   * add any DBRefEntrys to cdsSeq from contig that have a Mapping congruent to
+   * the given mapping.
+   * 
+   * @param cdsSeq
+   * @param contig
+   * @param mapping
+   * @return list of DBRefEntrys added.
+   */
+  public static List<DBRefEntry> propagateDBRefsToCDS(SequenceI cdsSeq,
+          SequenceI contig, SequenceI proteinProduct, Mapping mapping)
+  {
+
+    // gather direct refs from contig congrent with mapping
+    List<DBRefEntry> direct = new ArrayList<DBRefEntry>();
+    HashSet<String> directSources = new HashSet<String>();
+    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<DBRefEntry>();
+
+    // 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.
@@ -2013,7 +2175,7 @@ public class AlignmentUtils
     /*
      * 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
@@ -2022,7 +2184,7 @@ public class AlignmentUtils
     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;
   }
@@ -2298,7 +2460,7 @@ public class AlignmentUtils
      * are currently ignored here
      */
     String trans = codon.contains("-") ? "-"
-            : (codon.length() > 3 ? null : ResidueProperties
+            : (codon.length() > CODON_LENGTH ? null : ResidueProperties
                     .codonTranslate(codon));
     if (trans != null && !trans.equals(residue))
     {
@@ -2310,7 +2472,7 @@ public class AlignmentUtils
       // set score to 0f so 'graduated colour' option is offered! JAL-2060
       SequenceFeature sf = new SequenceFeature(
               SequenceOntologyI.SEQUENCE_VARIANT, desc, peptidePos,
-              peptidePos, 0f, "Jalview");
+              peptidePos, 0f, var.getSource());
       StringBuilder attributes = new StringBuilder(32);
       String id = (String) var.variant.getValue(ID);
       if (id != null)
@@ -2321,11 +2483,13 @@ public class AlignmentUtils
         }
         sf.setValue(ID, id);
         attributes.append(ID).append("=").append(id);
-        // TODO handle other species variants
+        // TODO handle other species variants JAL-2064
         StringBuilder link = new StringBuilder(32);
         try
         {
-          link.append(desc).append(" ").append(id)
+          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());
@@ -2334,8 +2498,7 @@ public class AlignmentUtils
           // as if
         }
       }
-      String clinSig = (String) var.variant
-              .getValue(CLINICAL_SIGNIFICANCE);
+      String clinSig = (String) var.variant.getValue(CLINICAL_SIGNIFICANCE);
       if (clinSig != null)
       {
         sf.setValue(CLINICAL_SIGNIFICANCE, clinSig);
@@ -2360,6 +2523,7 @@ public class AlignmentUtils
    * @param dnaToProtein
    * @return
    */
+  @SuppressWarnings("unchecked")
   static LinkedHashMap<Integer, List<DnaVariant>[]> buildDnaVariantsMap(
           SequenceI dnaSeq, MapList dnaToProtein)
   {
@@ -2403,7 +2567,7 @@ public class AlignmentUtils
         List<DnaVariant>[] codonVariants = variants.get(peptidePosition);
         if (codonVariants == null)
         {
-          codonVariants = new ArrayList[3];
+          codonVariants = new ArrayList[CODON_LENGTH];
           codonVariants[0] = new ArrayList<DnaVariant>();
           codonVariants[1] = new ArrayList<DnaVariant>();
           codonVariants[2] = new ArrayList<DnaVariant>();
@@ -2437,7 +2601,7 @@ public class AlignmentUtils
         /*
          * save nucleotide (and any variant) for each codon position
          */
-        for (int codonPos = 0; codonPos < 3; codonPos++)
+        for (int codonPos = 0; codonPos < CODON_LENGTH; codonPos++)
         {
           String nucleotide = String.valueOf(
                   dnaSeq.getCharAt(codon[codonPos] - dnaStart))
@@ -2490,7 +2654,7 @@ 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 +2665,8 @@ 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;
             }
@@ -2535,19 +2700,32 @@ public class AlignmentUtils
    */
   public static int alignAs(AlignmentI unaligned, AlignmentI aligned)
   {
+    /*
+     * easy case - aligning a copy of aligned sequences
+     */
+    if (alignAsSameSequences(unaligned, aligned))
+    {
+      return unaligned.getHeight();
+    }
+
+    /*
+     * fancy case - aligning via mappings between sequences
+     */
     List<SequenceI> unmapped = new ArrayList<SequenceI>();
     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())
     {
       if (!unmapped.contains(seq))
       {
         char[] newSeq = new char[width];
-        Arrays.fill(newSeq, gap);
+        Arrays.fill(newSeq, gap); // JBPComment - doubt this is faster than the
+                                  // Integer iteration below
         int newCol = 0;
         int lastCol = 0;
 
@@ -2569,7 +2747,7 @@ public class AlignmentUtils
           }
           newCol++;
         }
-        
+
         /*
          * trim trailing gaps
          */
@@ -2579,6 +2757,7 @@ public class AlignmentUtils
           System.arraycopy(newSeq, 0, tmp, 0, lastCol + 1);
           newSeq = tmp;
         }
+        // TODO: optimise SequenceI to avoid char[]->String->char[]
         seq.setSequence(String.valueOf(newSeq));
         realignedCount++;
       }
@@ -2587,6 +2766,72 @@ public class AlignmentUtils
   }
 
   /**
+   * If unaligned and aligned sequences share the same dataset sequences, then
+   * simply copies the aligned sequences to the unaligned sequences and returns
+   * 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,
+          AlignmentI aligned)
+  {
+    if (aligned.getDataset() == null || unaligned.getDataset() == null)
+    {
+      return false; // should only pass alignments with datasets here
+    }
+
+    // map from dataset sequence to alignment sequence(s)
+    Map<SequenceI, List<SequenceI>> alignedDatasets = new HashMap<SequenceI, List<SequenceI>>();
+    for (SequenceI seq : aligned.getSequences())
+    {
+      SequenceI ds = seq.getDatasetSequence();
+      if (alignedDatasets.get(ds) == null)
+      {
+        alignedDatasets.put(ds, new ArrayList<SequenceI>());
+      }
+      alignedDatasets.get(ds).add(seq);
+    }
+
+    /*
+     * first pass - check whether all sequences to be aligned share a dataset
+     * sequence with an aligned sequence
+     */
+    for (SequenceI seq : unaligned.getSequences())
+    {
+      if (!alignedDatasets.containsKey(seq.getDatasetSequence()))
+      {
+        return false;
+      }
+    }
+
+    /*
+     * 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())
+    {
+      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(alignedSequences.get(0).getSequenceAsString());
+      if (alignedSequences.size() > 0)
+      {
+        // pop off aligned sequences (except the last one)
+        alignedSequences.remove(0);
+      }
+    }
+
+    return true;
+  }
+
+  /**
    * Returns a map whose key is alignment column number (base 1), and whose
    * values are a map of sequence characters in that column.
    *