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Author | Topic: Different numbers of chromosomes? | |||||||||||||||||||||||||||
Ryan Bibler Inactive Member |
I have a question for the biologists in the group. How exactly can a new species end up with a different number of chromosomes than the species from which it descended? For example, hares have 24 pairs of chromosomes, while domestic rabbits have 22 and cottontails have 21. Back when I was a creationist, I would use this discrepancy as an argument against macroevolution. I'm just curious about the mechanism of how this works, thanks.
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Coragyps Member (Idle past 1051 days) Posts: 5553 From: Snyder, Texas, USA Joined: |
I'm not a biologist, but...
one excellent example of this is that all the great apes except humans have 24 pairs of chromosomes, while we have 23 pair. Our chromosome 2, though, looks exactly like two great ape chromosomes fused end-to-end - it even has the remnants of a spare centromere and two telomeres in its middle. Yunis, et al, in Science, 208, 1145-1148 (1980) have very nice pictures of this, but they are also on the web somewhere - Internet Infidels discussion board for one place, with "Scigirl" (from Bozeman!) explaining them. It seems pretty reasonable that a rare fusion event like this might not be a big obstacle to reproduction, either: unfused chromosomes from one gamete should pair right up with a fused version. It might get tricky when the zygote tried to divide, but hey - it only had to happen once.
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
Dear Coragyps,
For a elegant falsification go here: http://www.europa-universalis.com/forum/showthread.php?th... It is a bit much, but the final page says it all. Best wishes,peter
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Peter Member (Idle past 1796 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
Whenever this issue raers its ugly head I always
say look up Down's syndrome. I'm not sure exactly why or how such a thing happens,but Down's syndrome individuals have a different number of chromosomes to their parents, and most are fertile. That means it's possible for chromosome numbers to changewithin a population. |
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Quetzal Member (Idle past 6189 days) Posts: 3228 Joined: |
Hi Ryan,
There are a number of possibilities - chromosome fusion being one of them. Polyploidy (chromosome doubling) can also happen, although it's waaay more common in plants than in animals. As long as the mutation/doubling doesn't present a reproductive barrier, then the organisms are usually still considered the same species. The point is "species" is something of a squishy term - most are composed of discrete populations (called demes on the genetic level, or clines on the population level), that blend into each other where these populations overlap. If you'd like to look up further references, and have access to a decent library, here are three articles that you might find interesting from the journal Heredity: Castiglia, R and Capann, E wrote a series of three articles for the journal Heredity describing this observation:Contact zones between chromosomal races of Mus musculus domesticus. 1. Temporal analysis of a hybrid zone between the CD chromosomal race (2n=22) and populations with the standard karyotype. Heredity. 1999 Sep; 83:319-26 Contact zone between chromosomal races of Mus musculus domesticus. 2. Fertility and segregation in laboratory-reared and wild mice heterozygous for multiple robertsonian rearrangements.Heredity. 2000 Aug; 85:147-56 Contact zones between chromosomal races of Mus musculus domesticus. 3. Molecular and chromosomal evidence of restricted gene flow between the CD race (2n = 22) and the ACR race (2n = 24).Heredity. 2002 Sep; 89:219-24. If you're lazy (like me ![]() If you have any further questions, let us know. Happy reading!
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derwood Member (Idle past 2193 days) Posts: 1457 Joined: |
I posted what I reproduce below in response to the post by "Ilion" that borger links to. Ilion, like Borgewr, is an admitted 'darwin attacker' and non-scientist. As is Ilion's custom, he ignoirewd the falsification of his claims:
quote:
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
That was not the point, Page, and you know it. The point was that the mechanism between fusion and transloctaion are distincly different.
And you evo-guys put them on the same pile. Why do I still discuss with you, while you do not even understand molecular biology mechanisms? You are far out of date. I recommend you to buy yourself a recent biology book! And read it! Best wishes,Peter
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mark24 Member (Idle past 5512 days) Posts: 3857 From: UK Joined: |
You gotta be shittin me?
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
That's it?
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mark24 Member (Idle past 5512 days) Posts: 3857 From: UK Joined: |
Peter B,
Why not? You bailed on the intermediate fossil thread, & still think you have credulity re. Fossils, so I can reasonably ask, "that's it"? Mark ------------------Occam's razor is not for shaving with.
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
bailed out? I still wait for your reply.
Best wishes,Peter
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Mammuthus Member (Idle past 6792 days) Posts: 3085 From: Munich, Germany Joined: |
You are in absolutely no position to criticize the educational background of anybody Peter..you are the most poorly informed biology Ph.D. I have ever encountered...but then you do medical research so that explains a lot
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
Hi Mammuthus,
The 'Page Lane' is a dead end alley. You didn't know that? Best wishes,Peter
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Mammuthus Member (Idle past 6792 days) Posts: 3085 From: Munich, Germany Joined: |
PB: The 'Page Lane' is a dead end alley. You didn't know that?
PB: "Why do I still discuss with you, while you do not even understand molecular biology mechanisms? You are far out of date. I recommend you to buy yourself a recent biology book! And read it!" M: So you mean you are retracting this post of yours to Mark24? Glad to hear it. My post was accurate, you are the most poorly informed Ph.D. I have ever encountered...a personal observation not an insult....my jibe at medical geneticists was a joke. As to dead ends....you are the expert at that, MPG, GUToB, creatons, morphogenetic fields, evolution is only about the origin of genes (microbe to man..etc) regardless of what real evolutionary biologists say.
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peter borger Member (Idle past 7982 days) Posts: 965 From: australia Joined: |
Mammuthus: As to dead ends....you are the expert at that, MPG, GUToB, creatons, morphogenetic fields, evolution is only about the origin of genes (microbe to man..etc) regardless of what real evolutionary biologists say.
PB: GUToB it's not only the end, it's also the start. Best wishes,Peter
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