Transcript mapping. Figure (A) The two mtEST sets (EL and ES) mapped on a hypothetical mitochondrial genome. Each green or brown rectangle represents a single contig. The numbers indicate the number of ESTs building each contig. Curved lines indicate the presence and positions of the polyadenine tails. Alternative polyadenylation sites and transcripts spanning two genes are retained. (B) The position of consensus mtESTs against a Mytilus circular mitochondrial genome. There are no sequence differences between apparently alternatively polyadenylated transcripts. Note that these mtESTs were further trimmed to the common coverage before performing comparative analyses.