There is something wrong with this description.
As far as I know AA causes Sickle cell Disease and TT is the most common and normal genotype.
Checking the last release of the 1000genomes I got the following results, which means most part of individuals are TT(normal) for this SNP and only a few are AA (with sickle cell disease).
extracted from last release of 1000genomes
11 5248232 rs77121243 T A 100 PASS VT=SNP;SNPSOURCE=LOWCOV,EXOME;AN=2184;LDAF=0.0222;AC=49;AVGPOST=0.9996;THETA=0.0006;ERATE=0. 0003;RSQ=0.9950;AA=t;AF=0.02;AMR_AF=0.01;AFR_AF=0.09 GT:DS:GL
- SNPedia predates the 1000 genomes project, and tends to use dbSNP as the primary authority for SNP information. In this case, there is a subtle difference in how those two sources describe the same thing. I've updated the page rs334 to clarify the source of confusion, namely that this snp is an ambiguous flip on the minus strand. I've used this as an opportunity to add 1000 genomes links to the right hand side box on every rs# page. If you have further questions about this snp or others, please continue to make edits or contact us more directly as email@example.com --- cariaso 00:38, 21 December 2011 (UTC)