Question

Consider the following allele frequencies for three SNPs

	SNP1	SNP2	SNP3
Africa	A:20%,T:80%	G:70%,T:30%	C:20%,A:80%
Asia	A:50%,T:50%	G:20%,T:80%	C:20%,A:80%
South America	A:60%,T:40%	G:80%,T:20%	C:70%,A:30%

Where is this person from?

1) SNP1:A,T

2) SNP2:T,T

3) SNP3: A,A

Can someone please help me? Explaining all the steps. I don't know what to do. Thank you!

Answer 1

The person is from Africa. The logic goes as :

1. SNP1:A,T - 50:50 is ruled out because equal. From remaining 20:80 and 60:40, the difference in minor and major allele is more in 20:80. So, Africa origin. (In SNP allele frequency, the allele with low frequency is minor and that with high frequency is major allele).

2. SNP2:T,T - no conclusion can be drawn because SNP is for G,T.

3. SNP3:A,A - no conclusion can be drawn because SNP is for C,A.

So, the person is from Africa.