When I retrieve a complete exon list from the UCSC Genome refseq genes (human reference genome), I often find a single exon (same coordinates defined by chromosome number and start/end nucleotides) listed multiple times, i.e. with multiple genes defined by NM_ numbers. Is this to be expected? I realize that are instances of exons that are shared across multiple "genes," but there seem to be far too many instances of this in the sequence list and data tables to be due to actual shared exons alone.
Thanks. I'll have to check to see if there's a match with the number of transcripts or not.