The Incredible Shrinking Genome 113
Shipud writes "Mammalian genomes have been shrinking for about 65 million years, roughly since the dinosaur extinction. Why? And why were ancient mammalian genomes three times larger than they are today? A new article in Genome Biology and Evolution tries to explain this bizarre finding, and why the genomes of mammals (but not of other living groups) are still shrinking. 'Once [the dinosaurs] were gone, mammals started to radiate, fill those niches, and a whole new level of competition arose. The selective advantage of not having a genome encumbered by potentially damaging mobile DNA elements has probably become critical at this "be ye fruitful and multiply; bring forth abundantly in the earth, and multiply therein" stage. In effect, the genomes of mammals has been shrinking by removing mobile DNA elements, just after the KT boundary. And according to the model presented in this study, this process is still ongoing: mammalian genomes are not at an equilibrium size. Unlike flies, mammals are still cleaning up.'"
Comment removed (Score:5, Informative)
smaller code size without copy& paste (Score:5, Informative)
Body temperature control is very effective in reducing the number of different enzymes that need to be coded for.
Frogs, for example have ~8x more genes than humans - partly because they have lots of different enzymes that do the same thing but at different temperature.
Actual paper (Score:5, Informative)
Here's [oxfordjournals.org] the actual scientific paper, rather than the blog.
Ameoba is ten times larger than human (Score:5, Informative)
Size does not matter.
Re:entropy is winning (Score:5, Informative)
Devolution is indeed still evolution in some way.
But I think by evolution we mean progress too something 'better' and devolution too something 'worse'.
While I'll leave defining better and worse as an excercise to the reader (try finding a concencus on thatone).
Evolution doesn't make any value judgement other than: if it survives and reproduces, it's good. If it dies before reproduction, it's bad. In that sense, there's no such thing as evolution towards something worse. No matter how degenerate an organism may seem to you, it's like that because that's what works in that particular niche.
Re:entropy is winning (Score:4, Informative)
On the other hand, a shorter DNA strand has less room for errors that might be non-life threatening.
Meaning duplication errors are magnified.
No, the odds of any given base pair being transcribed incorrectly is the same regardless of how long the chain of DNA is. Thus you will have exactly the same numbers of errors in vital genes as you would if mobile DNA is thrown in around those genes.
Genome size (Score:5, Informative)
Sounds like you are insecure about your shrunken genome!
Meanwhile back in reality, here's some statistics
http://www.genomesize.com/statistics.php [genomesize.com]
Re:smaller code size without copy& paste (Score:3, Informative)
> Global warming is very recent.
No. Lady Gaea has done the global warming (and global freezing) thing quite a few times.
The current global warming trend (which is what is generally meant by the phrase) is very recent. In the last 65 million years, I bet the earth has several times been warmer than it is now.
Not quite. (Score:3, Informative)
A bigger genome != a more complex organism. What we seem to be finding is all sorts of funky ways for genes to be expressed. For those here who don't know, this is incredibly cool and froody. All that DNA formerly regarded as "junk" seems to be no such thing. We share lots of DNA sequences with rats and cockroaches, but expression is what counts.
But if you really want the ultimate in compact DNA with obfuscated (and self-modifying) code, I would recommend viruses. (Incidentally, a significant portion of our own DNA is of viral origin.) If there were a god, viruses would be my foremost evidence for its existence. And that god would definitely have to qualify as a really l337 geek.