Question

In which of the following human disorders is there a defect in the X chromosome?

• A. Hemophilia
• B. Down's syndrome
• C. Klinefelter’s syndrome
• D. Thalassemia

Hint:

X-linked disorders are those where the gene causing the disorder is located on the X chromosome. Hemophilia is one such disorder, causing problems with blood clotting.

Answer 1

The Correct Option is A

Step 1: Understanding X-linked genetic disorders.
X-linked disorders are caused by mutations in genes located on the X chromosome. These conditions typically affect males more than females because males have only one X chromosome.
Step 2: Analysis of options.

• (A) Hemophilia: Correct. Hemophilia is an X-linked genetic disorder where the blood does not clot properly, caused by a mutation on the X chromosome.
• (B) Down's syndrome: Incorrect. Down's syndrome is caused by an extra copy of chromosome 21 (trisomy 21), not a defect in the X chromosome.
• (C) Klinefelter’s syndrome: Incorrect. Klinefelter’s syndrome is caused by the presence of an extra X chromosome in males (XXY), but it is not caused by a defect in the X chromosome itself.
• (D) Thalassemia: Incorrect. Thalassemia is a blood disorder caused by mutations in the genes of chromosomes 11 and 16, not the X chromosome.

Step 3: Conclusion.
Hemophilia is the disorder among the options that is caused by a defect in the X chromosome. Final Answer:} Hemophilia.