In mice, the distance between the anus and genital opening (anogenital distance) is:

• A. Greater in the male than in the female
• B. Greater in the female than in the male
• C. Equal between sexes
• D. Variable with strain

Answer: (A)

Sexual dimorphism in anogenital distance reflects prenatal androgen exposure. During a critical prenatal window, androgens masculinize the perineal region, causing the distance between the anus and the genital opening to be longer in males than in females. This pattern is consistently observed across mouse strains, so AGD is used as a marker of prenatal androgen effects. Therefore, the distance is greater in the male than in the female. The other statements don’t fit because females do not have a longer AGD, the distances are not equal, and while absolute values can vary by strain, the sex difference remains the defining feature.