evolution of chromosome number

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jwalin
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evolution of chromosome number

Post by jwalin » Mon Dec 21, 2009 3:31 pm

hi
now there's a question on my mind if anytime there's been a chromosomal fusion would the length of a chromosome increase. yeah i think so.

anyways my main doubt is if 2 chromosomes fuse as is seen in human at chromosome number 2 and ( i don't know, if someone can answer well and good) then we will have 2 centromeres. have never heard anything of this sort before. then what happens? i think its just degraded or something but then how?
it isn't what you do that matters but it is how you do it

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Post by kolean » Mon Dec 21, 2009 3:58 pm

In the Wikipedia article on Human Chromosome 2, you will notice that it says vestigal centromere. If you wiki the word vestigal, then you will see that the centromere has homologous DNA sequence, but it has no function. They scan the DNA genome for homologous DNA sequences, and saw these parts match other parts, and came up with the theory of chromosomal fusion, or any of the other nonfunctional DNA sequences, as a possible consequence. Now with epigenetics, it is just not the DNA sequence that produce proteins, but the regulatory sequences too that help support expression of the proteins. Just because there is a similar centromere DNA sequence in the middle of the chromosome doesn't mean it functions as one. You would have to have regulatory genes within the centromere to make the spindle fibers attach to have it function like a true centromere during mitosis. Thus, there is all sorts of vestigal or even possible new genes within our DNA genome that is not expressed . . . yet.
This is in line with the concept that our spinal cords continued on and that at one time we had tails. We have a homologous DNA sequence within our genome, but it is not expressed . . . anymore (?). It is a vestigal structure. But it is only a theory, as we can not know for sure (has there been any long bones from the neanderthal age that survived? Do they have spinal bones? or has it only been skulls? anthropology is one subject I have not delved into . . yet :mrgreen: ).

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JackBean
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Post by JackBean » Mon Dec 21, 2009 8:36 pm

You can either join two chromosomes (in that case you need to silent one of centromeres) or break one chromosome into two (in that case, new centromere should appear).
If that does not happen, in first case your new chromosome will be earlier or later broken, because taken to opposite sites, in second case you would lose some piece of DNA. You can either survive that, probably with some difficulties, when missing several genes, or it can be simply lethal ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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