Discuss the role of heredity and prenatal biological influences in the development of sexual orientation.

Question

What will be an ideal response?

Answer 1

Heredity makes an important contribution to sexual orientation. Identical twins of both sexes are more likely than fraternal twins to share a homosexual orientation; so are biological (as opposed to adoptive) relatives. Furthermore, some evidence suggests that male homosexuality is more common on the maternal than on the paternal side of families, suggesting that it may be X-linked. According to some researchers, certain genes affect the level or impact of prenatal sex hormones, which modify brain structures in ways that induce homosexual feelings and behavior. Using genomewide testing methods with gay family members, researchers have begun to identify genetic markers linked to male homosexuality.
Girls exposed prenatally to very high levels of androgens or estrogens-either because of a genetic defect or from drugs given to the mother to prevent miscarriage-are more likely to develop lesbian or bisexual orientations. Furthermore, gay men tend to be later in birth order and to have a higher-than-average number of older brothers. Perhaps mothers with several male children sometimes produce antibodies to androgens, which reduce the prenatal impact of male sex hormones on the brains of later-born boys.