Coding vs Non-coding DNA

Question

[eva_u]

Hi all,

When we say that only about 1% of DNA is coding (i.e. for protein synthesis) what exactly are we counting??

As i understand there are genes, about 40000 of them, and about 25000 is coding... so that's definitely more than 1%...

I also tried counting base pairs: add up bp length of each chromosome ("all"); add up bp lengths of each protein-coding gene; then (all) - (protein-coding) = non-coding. Here i also got close to a 50-50 ratio.

So which elements of DNA are considered for this 99-1% ratio?

Here's where i got my numbers: https://www.encodeproject.org/report/?type=Gene&organism.scientific_name=Homo%20sapiens&searchTerm=gene&field=symbol&field=notes

https://archive.vn/20130414235101/http://useast.ensembl.org/Homo_sapiens/Location/Chromosome?r=1

https://www.ncbi.nlm.nih.gov/genome/annotation_euk/Homo_sapiens/108/

Thank you!

[eva_u]

Ah yes "gene" regions are not continuous exons. That makes perfect sense, thank you so much!

Answer 1

[GouthamAtla]

Its the number of basepairs of exons of all protein coding genes vs no. of basepairs in the genome.

Check the Summary section of this paper. Initial sequencing and analysis of the human genome

If there are 30,000–35,000 genes, with an average coding length of about 1,400 bp and average genomic extent of about 30 kb, then about 1.5% of the human genome would consist of coding sequence and one-third of the genome would be transcribed in genes

I guess needless to say, transcribed regions includes "introns, exons, UTRs etc" and coding regions includes only "exons", especially exons in CDS.