-Discontinuous regions can be selected by holding down [CTRL] and clicking on positions to add to the column selection. Note that each [CTRL]-Click changes the current selected sequence region to that column, but adds to the column selection. Selected columns are indicated by red highlighting in the ruler bar (Figure \ref{selectcols}).
+Discontinuous regions can be selected by holding down [CTRL] and clicking on
+positions to add to the column selection. Note that each [CTRL]-Click (PC) or
+[CMD]-Click (Mac) changes the current selected sequence region to that column,
+but adds to the column selection.
+Selected columns are indicated by red highlighting in the ruler bar (Figure \ref{selectcols}).