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Some people seem to have some misinformed views on haplogroups - namely, a seeming belief that they are hugely important on an individual's genetic makeup, perhaps even phenotype and race. This is just a brief thread to explain the actual value of haplogroups:
1) mtDNA constitutes the smallest chromosome in humans
mtDNA consists of only 16,600 base pairs, which might sound a lot but humans have around 3.2 billion, which means it's only about 0.0005% of your genome. In terms of direct impact on the physical form, mtDNA only constitutes 37 genes, of which according to wikipedia, 13 are for proteins (polypeptides), 22 are for transfer RNA (tRNA) and two are for the small and large subunits of ribosomal RNA (rRNA). It has very little effect on the individual. Remember, your eye colour alone is determined by c. ~15 genes, so 37 is a very small amount.
2) YDNA is larger than mtDNA, at about 50 million base pairs, but that's still only around 1% of the male genome (females do not have a Y-chromosome, which should tell you how important it is vis-a-vis phenotype and race). Unsurprisingly, it's mainly involved in proteins that exist in males but not females. It is a fascinating chromosome, especially with regards to the differences between humans and other mammals.
3) So why are they so often cited in human genetics?
Because they're the only genes automatically handed down father-to-son, and mother-to-child, excluding mutations, which makes them useful for identifying racial groupings. So if 80% of Britons are R1b, then R1b becomes associated with Britons. But, even assuming YDNA chomosome X is exclusively Finnish in origin, if someone has YDNA clade X, all it means is 1 great great great great great etc. grandparent was Finnish - and thus YDNA isn't hugely relevant in determine the race of an individual. Similarly, not being clade X doesn't mean you aren't Finnish, it just means your great great etc. grandparent wasn't Finnish. The remaining 99%+ of your makeup could easily be Finnish.
http://en.wikipedia.org/wiki/Y_chromosome
http://en.wikipedia.org/wiki/Mitochondrial_DNA
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