Detection of the Signature of Natural Selection in Humans: Evidence from the Duffy Blood Group LocusMartha T. Hamblin & Anna Di Rien
　
Resistance to the parasite Plasmodium vivax (causes Malaria) due to the reduced occurance of the "Duffy" surface antigen regoin in red blood cells in many Sub-Sarahan Areas causes a natural selection gradient for many African Americans. The Duffy blood group has three main alleles,(which are the alleles needed for inorder to become infected with Malaria) FY*A, FY*B, FY*O are at the highest frequency in Asia and Pacific Areas, intermediate in the Europeans and Americans, while it is at its lowest frequency in the Sub-Saharan ares resulting in increased resistance to Malaria. It is thought that there has been a huge positive impact of natural selection othese particular groups of alleles. 　

Individuals that are homozygous for the FY*O allele are completely immune to Malaria because Plasmodium vivax can only bind onto the Duffy blood group, which is located on the surface of red blood cells. It is said that the sub-saharan populations have aquired a FY*O homozygous mutation, which has resulted in Africans being Immune from Malaria. Directional natural selection has been the cause for this recent trend in the genetic resistance to Malaria in Africans. 　

The Duffy allele frequency variations of five populations in sub-saharan African were observed as well as 17 individuals from Italy. PCR (Polymerase Chain Reactions) were performed on all genomes inorder to analyze the sequence variation of the FY*A, FY*B, FY*O alleles. A two-step PCR process was used to analyze the Duffy Gene region and the FY*O variation in Africans compared to Europeans. it was found that all of the Africans being studied were homozygous for the FY*O allele while the 17 Italians only carried the FY*A & FY*B alleles. 　

Inconclusion, there is ample evidence to show that there has been directional selection being acted upon the Duffy gene regoin which further makes African more resistance to Malaria than other ethnicities. is is unsure if Plasmodium vivax pure existance is the cause of the FY*O fixation in Africans but it definitely a prominent factor.　
Shana Alderman
Literature Cited:
1. Hamblin, M.,T.Rien, A.,D. 2000. Detection of the signature of natural selection in humans: evidence from the duffy blood group locus. Science Direct. 66 (5): 1669–1679.