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Re: primers

Gautam Majumdar wrote:

But they tested only a small fraction of the mitochondrial DNA. Physical
characteristics are determined by somatic genes. Though mitochondrial
DNA is supposed to mutate faster than somatic DNA,

I don't believe it is completely true to say that all mitochondrial genes mutate faster than somatic genes. Many of the genes responsible for cellular respiration (subunits of NADH dehydrogenase, cytochrome c oxidase, ATP synthase) are located on the mitochondrial genome. Some of these mitochondrial genes are highly conserved, probably because their function is so crucial that it precludes too much tinkering with the polypeptide sequence of the final protein product. On the other hand, the D-loop region of the mitochondrial genome is highly variable; but it does not code for a protein.

Also, since mitochondria are maternally inherited, you typically only get one version of each mitochondrial gene - from the mother. Non-autosomal somatic genes, in contrast, can have both recessive and dominant versions (alleles), and so a "bad" allele (one that reduces fitness) can be covered up by the "good" allele, allowing the former to be propagated in a species. For the most part, this option is not open to mitochondrial genes, so "bad" mitochondrial genes are weeded out in a very direct way.