I am looking at the mouse reference genome in combination with ensemble annotation and am finding many transcripts that have no start codon.

For example, the transcript ENSMUST00000193149 at position 165503943-165567747. The first CDS has a frame number 1. In the UCSC genome browser, I see that in one of the tracks ADCY10 gene starts at this location, but in the protein sequence, there is an X under the first base, followed by a T under the next three (which indeed correspond to T).

I am puzzled: why does the transcript start at something other than the start codon? Why does the annotation indicate its start position as 165503943 instead of 165503944 where the actual codon starts?


1 Answer 1


The entry in ensembl has a "CDS 5' incomplete" tag



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