Doctors In Da House: Is There Sa Genotype

Doctors on nairaland is there anything like SA genotype. my friend says he's SA i dint believe but he says its true. Wat's d implication of having such genotype. When I look @ him sometimes i feel he might have some kind of disease. He's ma good friend and i really wish to know wat the so called SA genotype is about. please can u give me a detailed info on it. please doctors in d house. thanks