But one sentence jumped out at me:
“If you look at the chimpanzee genome and the human genome, the protein coding regions are, like, 98 percent, 99 percent identical,” she says. “But the junk DNA part is very, very different.”
You've heard that 98% stat over and over again, haven't you? But unless you dig into the details, you never learn that said "98%" covers only 1.5% of the DNA. I'd never dug into it before myself. I need to be more suspicious--I figured it was just a matter of complexity. Nope, hubris: "If we don't understand it, it doesn't matter."
I also did not know that. I had guessed, based on nothing whatsoever, that the junk DNA (which I will now know to call "satellite DNA") was going to turn out to be a repository of stuff to borrow in response to changing environments in some epigenetic programs. Guess I wasn't even close.
ReplyDeleteInteresting stuff.
Assistant Village Idiot: junk DNA (which I will now know to call "satellite DNA")
ReplyDeleteSatellite DNA is just one type of so-called junk DNA, or non-coding DNA.
james: "Junk DNA" has a purpose, something most of us probably guessed was true from first principles
Some DNA may not have any direct biological function, such as broken genes. Some may have a function not for the benefit of the organism, such as endogenous retroviruses. From first principles, some non-functional sequences should accumulate, even in highly optimized genomes, such as bacteria. The largest estimate is that 80% of the human genome is functional, but that is largely disputed.
On the other hand, it's been known for a while that portions of non-coding DNA must have a biological function as they are evolutionarily conserved. For instance, see Hardison, Conserved Non-Coding Sequences are Reliable Guides to Regulatory Elements, Trends in Genetics 2000. Similarly, sequences that have an evolutionary history of non-conservation suggest lack of function.