The frequency of homosexuality in men is highest if ____.
A) a sister is homosexual
B) an adopted brother is homosexual
C) a dizygotic twin brother is homosexual
D) a monozygotic twin brother is homosexual

Question

Quizplus · Accepted Answer

Several studies have shown that the frequency of homosexuality in men is highest if they have a monozygotic twin brother who is homosexual. This suggests a significant genetic component to sexual orientation. Studies have also shown that homosexuality is more common in siblings of gay men, but the effect is stronger for monozygotic twins.

The Frequency of Homosexuality in Men Is Highest If ____