Raphaël Champeimont has a blog called The Purple Blog: Freedom and Technology. His latest post is called The great Pufferfish Genome and it's well worth a read. Here's an excerpt ...
Human: I am the mighty human, pinnacle of the evolution: I have the most advanced and complex genome with 25,000 genes and an impressive 3 billion base pairs in my DNA, you know these letters like A, T, G, C which make my genome. 3 billion of them!
Pufferfish: Come on. Your genome is just full of junk, 90% of it is completely useless! It’s full of dead viruses that infected your ancestors long ago and you never cleaned it up. Look at my genome, I have just as many genes as you, but I don’t need to waste 3 billion base pairs of DNA for that, just 400 million is well enough. Yes, I pack as many genes as you in a genome 10 times smaller! That’s what I call optimization!
I met Raphaël a few months ago at a Café Scientific meeting in Mississauga, Ontario (Canada) and he came to our meeting last night. Turns out, he read my book and that's why he posted an article about genomes.
I recently read a very interesting new book “What's in Your Genome? 90% of Your Genome Is Junk” by Laurence A. Moran, in which he argues that our knowledge of genomics points to the fact that 90% of the human genome is useless junk.
This idea is not new, but it has become unfashionable in the last 20 years, without good evidence, the author argues. Most of our genome is still junk, and a central argument is that many other species don’t need that much DNA, or have much more without any “good” reason like the organism’s complexity.
I've lost count of how many people have read my book. I think this makes six or maybe seven!
I not only have read it, but I believe you are correct, and I have written about junk DNA based on your book and found that for the first time I had to have a part 1 and part 2!
ReplyDeletehttps://www.truthfulorigins.info/post/junk-dna-and-encode-part-1
I understand why onions, humans, and lungfish can have enlarged genomes full of various amounts of junk DNA. This being the result of neutral genetic drift. Meanwhile, the small genomes of yeast is also explainable, since their microbial ecology is one of tight energy budgets and short generation times. But why would the Pufferfish have a reduced genome? I can't think of a reason other than that genetic drift is "drifty". Sometimes drift wanders downward more than upward.
ReplyDeleteWhile I agree with you and Raphaël I have problems with the DNA which seemingly changes from left- to right-handed in the displayed picture.
ReplyDeleteAhah that's an AI-generated picture and it did not get it fully correct indeed.
DeleteThe presence of large amounts of junk DNA is neutral in the sense that natural selection is ineffective in reducing it. It is ineffective in effectively opposing forces such as infection of the genome by transposons. Just saying "the result of genetic drift" makes it sound like a base was added here and there by accident and piled up to be vast amounts of junk DNA. Correct me if I'm wrong, Larry, but spread of a transposon family is not like that at all.
ReplyDelete@Joe Felsenstein
ReplyDeleteGenomes can expand in size by segmental duplication or transposon insertion, among other things. In both cases, a new allele is created with extra DNA that was not present in the original genome at that locus.
The fate of that new allele in the population is determined by selection or genetic drift. If the new allele is effectively neutral then it could become fixed by random genetic drift.
@Larry: It was my understanding that active transposons infect both haploid genomes and therefore have a 2x advantage, which is strong genomic drive (or "meitoic drive") in their favor. Much more rapid spread in the population than mere drift.
ReplyDelete... and in addition of course, once an active transposon is in a genome, it makes copies of itself at other places on both haploid genomes. So in effect it creates mutations to itself.
ReplyDeleteLet me be more accurate: meiotic drive systems may copy a stretch of chromosome to all gametes, rather than the 1/2 of them that normal Mendelian segregation does. Active transposons result in an increase of copies in all the gametes, though located in many different parts of the genome. Considered for the whole genomes of descendants, an increase of copies far faster than would occur just by genetic drift, with the loss of the transposon from the genome much less likely than with mere genetic drift.
ReplyDelete