This is the main question that is lurking the minds of biologists for quite some time now because many possibilities for the occurrence of a homosexuality gene exist. During the 1990s many researcher were studying the topic but by the end of the 20th century all such research work was slowed down as many people are shy when they are asked on topics related to sex and specially homosexuality. Scientists Sergey Gavrilets and William Rice have developed some guidelines for explaining the causes of homosexuality. During the past decade the scientists have discovered some patterns that might point to genetic causes of homosexuality. Among the discoveries the main finding was that in case of male homosexuality it seems to be inherited more from the mother than the father and the female maternal relatives of gay men have higher that average reproduction capacity. Another shocking discovery was that the chances of homosexuality increases in males with the number of older brothers he has even if the child has grown up away from his brothers. The reason for this is that the with each male fetus the mother develops an increased immunization to an antigen that is produced by male fetuses and this antigen plays an important role in masculinizing the brain. All the studies have strong evidences that homosexuality is caused by a gene but no research has pointed to any specific gene and the idea to which each research points is towards a polymorphic gene. Rice commented that, ‘We know that homosexuality (gay or lesbian) can be caused by simple genetic changes in fruit flies, and since so many reproductive and neurological genes are shared by flies and humans, it seems highly likely that there are major genes influencing homosexuality in humans, However, we also have firm evidence for a birth-order effect on male homosexuality, and discordance in the expression of homosexuality of identical twins, so clearly there is also an environmental influence on the trait.’ This research is the most guiding research on the topic, though it also has not pointed out any particular gene but this will be the backbone of all future researchers that can one day tell us the exact cause of Homosexuality.

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