Hacker News Reader

Comment by kitd | Hacker News Reader

OK, I'm not any kind of expert in this area, but is RNA not considered an early form of genetic coding? And DNA evolved from it? Also, don't viruses replicate by "borrowing" the mechanism of their hosts?

My understanding is that life visible to the naked eye is a minority of life forms on the planet. Maybe other forms of genetic coding than DNA are more prevalent than we anthropocentrists think.

View on HN

My own tin-hat theory on that is DNA probably co-evolved with RNA pretty quickly. The main difference between RNA and DNA is that a single RNA strand can fold up and bond with itself to make interesting() 3d shapes while DNA can't self-fold. I think single-stranded DNA initially served as a durable, robust structure for RNA to assemble against before it went off and folded up and did whatever it did chemically. This might help explain why RNA polymerase only runs 3'->5'; in fact one of the early functions of one of the RNA polymerase components was maybe to keep the single DNA strand "tidy" and free of random base-pairings. Also, it might help explain why the 3'->5' DNA strand has to jump through so many extra hoops to get replicated - double-stranded DNA came later. It might also explain the reason reverse transcriptase exists at all. Again, I am probably provably a crank on this.

() This is the whole appeal of the "RNA world" hypothesis, you have one molecule that can serve both as "code" and catalyst for other chemical reactions.

Yes. DNA probably "evolved" from RNA. Keep im mind that the time scale is huge and that at the time, the earth was really hot and pressurized, so we can only have speculations.

A posituve thing is that in Miller experiment, he found out that those conditions create aminate acids. That also indicate that panspermia theory is unlikely (not impossible, but not Occam's razor choice at least).

Reply on news.ycombinator.com