Hey guys I used igv to check a WES bam file. When I looked to EGFR gene, I saw that the refseq genes with blue thicker bar had a better coverage of reads. However there is little read on the blue thinner bar region.

I thought all blue bar region was exon. Now I don't know whether I am right.

So, the question is: 1, Does the whole blue bar mean exon region? What the exact mean of thicker bar and thinner bar？ 2，Why the blue thicker bar has a better coverage ？Please help me find some possible reasons.

Thanks everyone！