The genes a man gets from his mother and father may play an important role in determining whether he is gay or not, according to a new study likely to reignite the “gay gene” debate.Researchers say it’s the first time the entire human genetic makeup has been scanned in search of possible genetic determinants of male sexual orientation. The results suggest that several genetic regions may influence homosexuality. “It builds on previous studies that have consistently found evidence of genetic influence on sexual orientation, but our study is the first to look at exactly where those genes are located,” says researcher Brian Mustanski, PhD, a psychologist at the University of Illinois at Chicago.Those previous studies looked only at the genes located on the X chromosome. Genes on this chromosome are only passed to a son from his mother. But this study examined genetic information on all chromosomes, including genes from the father.The findings show that identical stretches of DNA on three chromosomes were shared by about 60% of gay brothers in the study compared to the about 50% normally expected by chance.
