Talk:Chromosome

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I've got a Question for the Evolutionists here. (I really would like a serious Answer so perhaps we could put the abuse somewhere else for a while.) I started thinking about this after reading the Humanzee article and its Talk Page. It seems that Animals which mate with other animals with a different Number of Chromosomes are almost always Infertile. Humans have 46 chromosomes and chimpanzees 48, consequently the imagined Last Common Ancestor of Chimps and Humans presumably had either 46 or 48 (or maybe even some other Number it doesn't matter for the question.) So at some point an Individual must have been born with a number of Chromosomes Different from his parents and his siblings.

• With whom would such an animal mate and produce improbable Fertile Offspring?
• How many Chromosomes would they have?
• How would they mate in such a way as to Maintain the new Chromosome number and not have it Disappear back into the general population?--Tolerance 13:45, 15 April 2009 (EDT)

Good question, one that I had some months ago. It depends very much on the type of chromosomal change. Simply deleting or duplicating a chromosome will normally end badly (Downs, et al), but translocations are a different story. If translocation occurs: a quantity of a chromosome is split off to form a new one, or conversely, you have a fusion of two (as in our genetic past), it's quite possible to interbreed (as many horses do), as translocated and non-translocated chromosomes will pair up (they still contain the same quantity of information, despite different chromosome count). PZ Myers has a far more indepth, crayon-drawn explanation here [1]. 14:11, 15 April 2009 (EDT)

If it helps, the chromosomes that are different are actually fused together. So in reality, the genetic materials aren't as different as saying "oh, there's a chromosome missing! How does that work then?" that I'm sure most people may immediately think.

http://www.indiana.edu/~ensiweb/lessons/c.fus.les.html

http://www.teachersdomain.org/resource/evol07.sci.life.evo.genconnect/

Basically, evolutionary theories predicted that this sort of thing would happen, and the tests showed it. ArmondikoV^narchist 14:24, 15 April 2009 (EDT)

Interesting. Thank you for responding. I shall click the links. However I think I should point out that you don't seem to have respondd to the Third Question : 'How would they mate in such a way as to Maintain the new Chromosome number and not have it Disappear back into the general population?'

It seems that such animals will already be of doubtful fertility. Presumably, in a Darwinian world, their low Fertility and the fact they they would be massively outnumbered by "normal" animals would mean that their Chromosome mutation would be lost in the Herd. However I shall click your links as there may be a Darwinian Explanation there.--Tolerance 15:17, 15 April 2009 (EDT)

For the same reason any alteration to the genome will persist. Individual genes can just outcompete the others by either drift or selection, first on a small, local scale where an individual man or woman ends up producing most of the progengy and then a larger scale as that tribe/group expands outwards propograting that mutation.

As for guaranteeing fertility, if the overall material isn't similar, then a mismatched chromosome number can be either fatal or produce infertility. If the overall genetic information is nearly the same, then it's not so much of a problem and a lower chromosome count would probably be better for cell division such as mitosis and meiosis due to the way they're separated beforehand. ArmondikoV^narchist 15:25, 15 April 2009 (EDT)

I see the PZ Myers post also covers this point. Thank You both again.--Tolerance 15:26, 15 April 2009 (EDT)

Yes, that was one of the most interesting bits. Utterly benign/pointless changes can spread by simple virtue of chance (though few do), since the number of chromosomes is itself largely pointless and benign. 17:04, 15 April 2009 (EDT)

Handy diagram

That "handy diagram" would only actually be handy if it explained what those numbers meant. The key on the file page is in German. 109.204.116.189 (talk) (Sophie) 12:28, 4 December 2019 (UTC)