I am reading in notes for a comparative annotation lecture that :
- all DNA is subject to mutations
- most functional regions are under negative selection (ie., mutations are often deleterious)
The conclusion was:
that pieces of DNA with specific functions (especially genes) tend to be conserved against mutation more strongly than a DNA region with no specific function.
So if i understand it properly, since all DNA can accumulate mutations, the regions of genes that provide some fitness benefits avoid the negative selection of random mutations and are preserved (conserved?).
Also, the author placed in parentheses, (especially genes), therefore are there non coding regions that can provide benefits? Is he referring to "Selfish DNA" like Transposable elements that can have regulatory functions (or so i have heard).