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The Incredible Shrinking Genome
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.'"
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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.
Here's the actual scientific paper, rather than the blog.
Some have over a hunred billion base pairs. There a tremendous amount of junk DNA and gene duplication.
Size does not matter.
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.
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.
"bigger genome.... bigger mammals! that's it. The woolly mammoth was big because his dna was big! guess size does matter."
...
Sounds like you are insecure about your shrunken genome!
Meanwhile back in reality, here's some statistics
http://www.genomesize.com/statistics.php
There are 10 kinds of people in the world... those who understand binary and those who don't.