Which sex chromosome disorder is characterized by infertility and abnormal secondary sexual development in males?

• A. Down Syndrome
• B. Klinefelter's Syndrome
• C. Talipes
• D. Spina Bifida

Answer: (B)

A sex chromosome disorder can directly affect male development and fertility. Klinefelter syndrome happens when a male has an extra X chromosome (usually 47,XXY). The extra genetic material disrupts normal testicular development, leading to lower testosterone levels and impaired sperm production. That combination results in infertility and altered secondary sexual characteristics, such as less facial/body hair, smaller testes, and sometimes gynecomastia.

The other conditions don’t fit this pattern. Down Syndrome is due to an extra copy of chromosome 21 and involves intellectual and facial features rather than primary infertility or abnormal male sexual development. Talipes is a foot deformity, and Spina Bifida is a neural tube defect; neither involves sex chromosome–related effects on fertility or male puberty.