Woof !
Well, the evolution part of the class is over but I'm going to spend the next few days posting links to evolution related news from the last few weeks to show you what an interesting and dynamic science evolution is before we start on the next section. It isn't just a set of facts, although, for obvious reasons, that is how it can tend to come across in class.Up first is the evolution of the dog. (The photo is from CuteOverload - the only place to go when you need some cute.)
As we have mentioned several times Darwin was a very smart and perceptive guy. But when it came to dogs even Darwin underestimated the power of selection (here artificial selection rather than natural selection). Darwin thought that the current array of dog breeds must have been descended from a number of different wild canine species such as such as jackals, coyotes and wolves. We now know this is not the case and all 350+ distinct breeds are, in fact, descended from one species, the grey wolf. This raises the question of just where all the variety in dogs came from.
A paper in Genome Research on June 29th of this year by Matthew Webster of Trinity College Dublin, Ireland, and colleagues at Uppsala University in Sweden has proposed an explanation. They analysed the complete mitochondrial DNA genome in 14 dogs, six wolves, and three coyotes. This data suggests that mutations in the canine genome have played a bigger role in dog evolution than previously thought. Natural selection usually weeds out mutations in wild species if they offer no survival advantage. But if that pressure is removed, these mutations will get passed on. This provided dog breeders with a wide inventory of traits in the DNA to exploit. Others disagree, Webster et al. only studied mutations in mitochondrial DNA, which tends to accumulate more quickly than in nuclear DNA which forms the largest part of the genome. Far fewer mutations may have occurred in genes in the nucleus compared with mitochondria. Much of the variation we see in dogs may have to do with pre-existing variation from the ancestral wolf-dog population.
Labels: Evolution, Research Reports
posted by John Latto @ 7:22 PM
3 comments
3 Comments:
=D cute dog!
it's kinda hard to believe that in fact all dogs were once from the same looking ancestor (well of course they all came from the earliest prokaryotic things, but you get my idea).
What are mitochondrial DNA's?
At the end of that paragraph you said "far fewer mutations...nucleus compared with mitochondria...pre-existing variation...wolf-dog population." So, are you saying the mutations in the mitochondria DNA doesn't matter as much and only the ones in the nucleus do? So the dog variations are not even from later mutations but rather from earlier mutations in the wolves? Please clarify that part. Thanks! =)
yeah, i have that question about mitochondrial DNA too...
mitochondria repilcates independently and has its own DNA then what effect does it have on the cell as whole?
Mitochondrial DNA (or mtDNA) is the genetic material asscoiated with the energy producing mitochondria in the cell. The fact that it has its own DNA is evidence for the theory that mitochondria may have descended from free-living prokaryotic bacteria. We will discuss this in a later class.
Because mtDNA is thought to be inherited from the mother alone it is very stable from generation to generation (unlike nuclear dna which undergoes sexual recombination every generation). This makes it a very useful tool to study mutation rates because changes in the mtDNA can be assumed to be solely due to mutation.
The dog researchers used mtDNA to look at how mutations had accumulated in the mtDNA. IF the same process had occurred in the nuclear DNA then this would suggest that mutation has been an important source of the variation in dogs since the divergence from wolves. But, as I mentioned, that is a bit of a big if.
Post a Comment
<< Home