How has DNA accumulated a lot of non-coding DNA?

Expert Solution

DNA may comprise of coding sequences which can code for proteins, like the exons.

Many eukaryotic gene contain, regions of “expressed sequence” or exons, which code for proteins.

Non-coding DNA include positions of DNA which does not code for protein. These are more in eukaryotic genome.

Non-coding regions include intervening sequences or introns, regulatory sequences as operator, promoter, enhancer sequences and repetitive DNA sequences or repeats (tandem repeats, interspersed sequences).
The non-coding portions are generally removed during splicing.
But by variation in the splicing process, may retain some of the non-coding potions.
The process of alternative splicing, the gene products may be modified. In alternate splicing alternative introns may be removed to get a different sequence producing an alternative protein.
Thus, the sequences that are spliced, or the retained sequences after the splicing, will express differently specifying different cell types.
This differential splicing (alternative splicing) mechanisms result in accumulation of non-coding region in genome.
Transposable elements also contain some sequences that are duplicated on integration, resulting in repeats.

gladiator answered 2 years ago

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