I am trying to calculate the total exonic length (in bp) in order to see where the coding-noncoding ratio of roughly 1% to 99% comes from. We know all chromosomes total about 3 billion base pairs. So Is it correct to assume that coding regions would total about 30 million base pairs? I am looking at the numbers in the sources below, but nothing there adds up...

Take numbers from NCBI annothation for example; specifically

NCBI exon length

no matter how i count i can't get the expected ratio... What am doing wrong?

Thank you!



  • 1
    $\begingroup$ cross-posted: biostars.org/p/447675 $\endgroup$
    – burger
    Jul 7, 2020 at 0:59
  • $\begingroup$ There are a few different answers provided here: biology.stackexchange.com/questions/48110/… $\endgroup$
    – burger
    Jul 7, 2020 at 1:16
  • $\begingroup$ Thank you, but this is a different question; my aim is to get the said ratio given the feature numbers, in my case the length of coding vs non-coding regions. The original response helped me by pointing out that i should focus on exons, rather than the entire gene region. So i searched and found some definitive numbers for exon length, and calculated in different combinations, but they still aren't adding up to the 99%-1% ratio. So i'm wondering if i'm missing something else here. Or whether i'm looking at the wrong features entirely. $\endgroup$
    – janeu
    Jul 7, 2020 at 1:42
  • $\begingroup$ They are not adding up because you need exclude non-coding exons (non-CDS) and exclude overlapping features. The discussion I posted shows how to get coding regions. The only difference is that they are trying to get the average length and you need total length. $\endgroup$
    – burger
    Jul 7, 2020 at 3:00


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