Question

What does non-coding DNA do and where did it come from? What conflicting factors act to increase or decrease the amount of non-coding DNA?

Answer 1

Considering the human genome, only 1% of it is coding for proteins and 25% of it constitutes regulatory regions DNA! There are different functions performed by the remaining huge chunk of non-coding DNA.

a) they could be regulatory elements like gene repressors/ enhancers that regulate transcription, etc.

b) Many DNA sequences in the eukaryotes undergo splicing and the introns in general (~20%< 11000bp) in length compared to exons (~200bp).

c) noncoding RNAs like tRNA, rRNA, snRNA, miRNA, piwi RNAs coding regions

d) Long non-coding RNAs in with gene regulatory roles.

e) pseudogenes are genes that got inactivated as a result of mutations that remain as non-coding DNA.

f) Repeats of the same DNA sequences due to erroneous replication and error repair mechanisms.

Erroneous processes like gene duplication, sequence duplication, mutations inactivating a gene, etc can happen during cell replication, inefficient error repair etc. can contribute to increase of non coding DNA. Whereas the deletion of repeated regions of DNA could result in non coding DNA their reduction.