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Author Topic:   A race shares genes?
caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 6 of 19 (577788)
08-30-2010 12:02 PM
Reply to: Message 1 by Ragged
08-30-2010 9:36 AM


It makes sense for particular genes (I think it would be more accurate to say particular alleles of genes) to be more common in certain races than in the general population, just because people share more recent common ancestry with others of their race. It'd be a surprise for every one of them to have the same allele though, and it would be an allele that is present in the general population too, just at lower frequencies.
As an example, the mutation which causes Tay-Sach's disease is more common among Ashkenazi Jews than amongst other populations (just Ashkenazim, though - this doesn't apply to other Jewish populations around the world). Not all Ashkenazi have it, though, and it's found in non-Jewish people too. It's also common amongst people of Cajun descent, according to wikipedia, though it's unknown whether they inherited it from Jews or if the same mutation arose independently (it's an insertion of four base pairs, not a single point mutation, so I think this makes it unlikely to have arisen independently).

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(1)
Message 12 of 19 (577935)
08-31-2010 6:21 AM
Reply to: Message 10 by Ragged
08-30-2010 7:17 PM


Re: what about other races though
I am implying however that you could never confuse a person of an Asian race with a person from, say, an African race.
Of course you could. Without looking up the source of the pictures - which one's which?
People tend to share more genes with people who are more closely related to them - this much is obvious. But different traits have different distributions. Take a look at the maps on this page showing the distribution of the different alleles for blood groups around the world. It's a clear, regional distribution showing taht people are more likely to be similar to people near them than not. But it doesn't match up to any clear division of races. It's interesting to note, for example, that people from around the Ivory Coast, in the west of Africa, seem to have a very similar distribution of alleles to people from northern Siberia. Siberians don't look like Ivorians, and in lots of other genetic markers they'd be very different, but in this one they're similar.
There was a programme made for Brazillian TV, in which a bunch of celebrities agreed to have their DNA tested for markers of European, African and Amerindian ancestry. Brazil's a melting pot, so almost everyone's got a bit of each. One of the subjects was this singer, Neguiho de Beija Flor:
The guy's clearly got African ancestry, as we can tell from his skin colour and the shape of his face. Thing is, the estimate arrived at by the DNA analysis was that his ancestry was about 67% European. The obvious, external traits we think about when we think of race only account for a part of our genetic makeup, and the actual picture is much more complicated than any usual racial classification.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 19 of 19 (578207)
09-01-2010 4:49 AM
Reply to: Message 15 by Ragged
08-31-2010 4:20 PM


Re: what about other races though
Others have pointed out the idea I was trying to get across with these pictures. Both the Brazillian singer and the Filipino girl look quite typically black - dark skin, frizzy hair, broad nose etc. However, the Brazillian, despite his appearance, only received a minority of his genes from recent African ancestry - he's genetically more similar to pasty-white Europeans; while the Filipina has no recent African ancestry at all, to the best of our knowledge. The physical traits were arrived at independently due to climate and the odd quirks of history, and genetically she's likely to be about as different from African populations as you can get.
Many of our genes have little to do with the easy outward identifiers of race, so looking similar on the outside doesn't necessarily mean a close genetic relationship. There's always been gene flow between populations to complicate the picture, and in the last 500 years this has accelerated dramatically. To make things even more complex, similar looking traits have been arrived at wholly independently by populations in different parts of the world, as the various dark-skinned people of Asia and the Pacific show.
Edited by caffeine, : errant comma

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