Philosophical Musings

Philosophical Musings

Tuesday, March 14, 2017

Chromosomes & Equidae

I think an understanding of the chromosome & some of the terminology would be good to clarify. So much of the misunderstandings about genetics & living organisms are due to flawed beliefs about the DNA, how it is assembled, what it does, & how it can change. I noted in an earlier post that equids have an apparent ability to 'adjust' their chromosome number to produce more variety. You do not see this with canids, or hominids. They remain constant in their genetic line, or 'haplogroup'.
We have evidence that the equid line has changed chromosome numbers. It is theorized that at some point, a chromosome pair detached at the centromere, & reattached at a telomere, presumably at the fertilized egg level. We have mtDNA to indicate actual descendancy, but the chromosome pairs are different. But, under further examination, the structure of the chromosome 'arms' are the same, just rearranged at the centromere/telomere level.

This is not absolutely proven fact, but is merely a theory for HOW the equid line changed at the chromosomal level. it does fit with the more empirical evidence of mtDNA descendancy, however, so it is a pretty good theory. But, we do not see a lot of the same thing with canids.. some, but not as much. Nor do we see it with hominids, especially humans. So a particular trait from one genotype does not mean it can be universally applied to ALL genotypes. Each genomic structure is different, with different rules governing their propagation.

Also, as i noted in the earlier post, the number of chromosomes is not an indicator of ancestry. 

Here are some chromosome pairs numbers from wiki:
Fennec fox [​IMG] Animals Vulpes zerda 64
Horse [​IMG] Animals Equus ferus caballus 64
Spotted skunk [​IMG] Animals Spilogale x 64
Mule [​IMG] Animals 63 semi-infertile
Donkey [​IMG] Animals Equus africanus asinus 62

We have mtDNA evidence that asinus & caballus are related. But there is nothing to indicate any genetic relationship with the fox or skunk. So the mere number of chromosomes is not a significant indicator, but the GENETIC structure in it, is. Both the asinus & caballus are from the same root haplogroup.. they are descended from the same ancestor. Their genetic STRUCTURE is the same. the fox & skunk are not. They are a different genotype, from a different haplogroup.

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