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Author Topic:   Chromosomal evolution
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 6 of 7 (357946)
10-21-2006 12:34 PM
Reply to: Message 5 by NosyNed
10-19-2006 1:21 PM


Re: Equine Chromosomes
Wild mountain zebras have 16 pairs of chromosomes, ...
That's quite a difference eh?
Compared to the other species it looks like polyploidy or something similar occurred at some point between WMZebras and other equines.
Zebroid - Wikipedia
quote:
A donkey has 62 chromosomes; the zebra has between 44 and 62 (depending on species). In spite of this difference, viable hybrids are possible provided the gene combination in the hybrid allows for embryonic development to birth. A hybrid has a number of chromosomes somewhere in between. The chromosome difference makes female hybrids poorly fertile and male hybrids sterile due to a phenomenon called Haldane's Rule. The difference in chromosome number is most likely due to horses having 2 longer chromosomes that contain similar gene content that contain the same genes as 4 zebra chromosomes.
So are there hybrids between the different zebra species? Are they fertile?
Seems to me that when there are fused chromosomes in some species closely related to others without the fusion, that they could - occasionally - have both of the non-fused versions match up to the one fused one in hybrids.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 7 of 7 (357948)
10-21-2006 12:44 PM
Reply to: Message 3 by kuresu
10-18-2006 4:53 PM


polyploidy in a number of species
and in rodents
Page not found - My Kratom And Weed Blog
and to answer codegate
quote:
Since fertility barriers likely isolated this tetraploid lineage from its ancestors, instantaneous speciation, although rare is possible in mammals, and a role for doubling series variation in genome size to trigger evolutionary novelties is suggested by this unique tetraploid rodent. Funded by Fondecyt 1970710 and the Fulbright Commission.
It certainly poses a problem for reproduction to have some paired chromosomes and some unpaired ones, as demonstrated by the numerous cases of infertile hybrids between species with only 1 or 2 differences in numbers.
Would it be possible for a tetraploid egg to be fertilized by two diploid sperm? A diploid egg to be fertilized by one tetraploid sperm and one diploid sperm? Both could generate matched pairs of chromosomes in the zygote that would now be also tetraploid without necessitating sibling mating.
Just my rambling thoughts.

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