Question

A disease caused by an autosomal primary non- disjunction is:

• A. Klinefelter's Syndrome
• B. Turner's Syndrome
• C. Sickel Cell Anemia
• D. Down's Syndrome

Answer 1

The Correct Option is D

To solve this question, let's first understand the nature and causes of each of the diseases mentioned in the options:

1. Klinefelter's Syndrome: This is a genetic condition that affects males who have an extra X chromosome (XXY). It is not the result of autosomal non-disjunction but rather a sex chromosome non-disjunction.
2. Turner's Syndrome: This condition affects females who usually have only one X chromosome (X0). Like Klinefelter's syndrome, it is a result of sex chromosome non-disjunction.
3. Sickle Cell Anemia: This is a hereditary disease that results from a single point mutation in the beta-globin gene, leading to abnormal hemoglobin. It is not caused by non-disjunction.
4. Down's Syndrome: Also known as Trisomy 21, this condition is caused by an extra copy of chromosome 21. This is a result of an autosomal primary non-disjunction, during which chromosome 21 fails to separate during the formation of the egg or sperm.

Conclusion: Based on the definitions, Down's Syndrome correctly matches as a disease caused by an autosomal primary non-disjunction, which leads to an extra chromosome 21 being present.