How well do we understand DNA?

There is some indication that sheer bulk of DNA carries some selective benefit. Bases added to DNA simply for the sake of bulk are legitimately called junk.Sample reference of many: Cavalier-Smith, T. Skeletal DNA and the evolution of genome size. Annu. Rev. Biophys. Bioeng. 11:273-302 (1982). Ref pinched from bibliography of Evolutionary Principles of Genomic Compression by David C. Krakauer.We also know that different parts of the genome have different selective pressures. Some sequences are highly conserved; others are not. In fact, this is one way of identifying sequences that have some importance, even if we don't know their role! One mystery is that some high conserved sequences were deleted from mice, with no apparent effect. This remains a mystery.Ref: Are Ultra-conserved Elements Indispensable? by Dr Mae-Wan Ho (ISIS press release, 16/09/04).But by comparison there are other parts of the genome where mutations accumulate at pretty much the same rate as they arise, indicating no selective pressures at work. This is indirect evidence for junk, I suggest.Cheers -- Sylas

This is an intriguing arguement by crashfrog, but flawed. The measure of 1 mutation per hundred base pairs per generation (actually, the real figure is more like 1 per 10⁸ base pairs) is itself a measure of a stochastic process. If you have a genome with 6 by 10⁹ base pairs, it means that you get about 60 mutations per generation. It could be more, and it could be less, but the average is 60.Crashfrog's argument assumes that the organism will have exactly that many mutations, and that is the error.Increasing genome length does not change the probability of mutations in the bits you care about.Cheers -- Sylas

No, no! Don't give up so easily! Damn... the creationists are more fun. Other folks keep learning stuff way too quickly. (Apologies to the creationists here who do learn things from time to time... I know the above is a cheap shot.)