Hello, Dan.

One of our engineers had this to say:

We do our own mapping of RefSeq sequences to the genome.  This gene maps to
19 different places in hg19 using our mapping procedure (some on chr4 some
on chr10, others on random chromosomes).  The procedure is documented here:

http://genome.ucsc.edu/cgi-bin/hgTrackUi?c=chr4&g=refGene

Blat will introduce gaps in the alignment if the sequence doesn't match the
genome.  We close blocks of 8bp or less when we make the gene models.

Please contact us again at [email protected] if you have any further
questions.

---
Steve Heitner
UCSC Genome Bioinformatics Group

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Dan Richards
Sent: Wednesday, January 25, 2012 1:59 PM
To: [email protected]
Subject: [Genome] How does UCSC hg19 gene model add exons to RefSeqs?

Hi, when using the human reference hg19 gene model, there are like this (in
GTF output format from hgTable Genes and Gene Prediction group, RefSeq Genes
track):

chr10   hg19_refGene    start_codon     135480472       135480474
0.000000        +       .       gene_id "NM_012147"; transcript_id
"NM_012147";
chr10   hg19_refGene    CDS     135480472       135481677
0.000000        +       0       gene_id "NM_012147"; transcript_id
"NM_012147";
chr10   hg19_refGene    exon    135480432       135481677
0.000000        +       .       gene_id "NM_012147"; transcript_id
"NM_012147";
chr10   hg19_refGene    CDS     135484982       135485230
0.000000        +       0       gene_id "NM_012147"; transcript_id
"NM_012147";
chr10   hg19_refGene    stop_codon      135485231       135485233
0.000000        +       .       gene_id "NM_012147"; transcript_id
"NM_012147";
chr10   hg19_refGene    exon    135484982       135485275
0.000000        +       .       gene_id "NM_012147"; transcript_id
"NM_012147";
where the hg19 model has an exon that does not exon exist in the RefSeq
accession (or any historical version of the RefSeq accession).

How/why does the alignment introduce an intron in this case? Does it ensure
there are plausible flanking splice junctions before inserting an intron to
a RefSeq sequence that lacks it but it maps to?

Dan
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