Q. Consider the following pairs:
DisorderGenetic Cause & Chromosome
1. Down’s SyndromeTrisomy involving an extra copy of Chromosome 21
2. Turner’s SyndromeMonosomy (XO) occurring in females
3. Klinefelter’s SyndromeDeletion of a segment of the Y chromosome in males
4. Cri-du-chat SyndromeDeletion of a part of the short arm of Chromosome 5
How many of the pairs given above are correctly matched?
Answer: C
Notes:
Explanation:
- Pair 1 is correctly matched: Down’s Syndrome is the result of Trisomy 21, where an individual has three copies of chromosome 21 instead of the usual two.
- Pair 2 is correctly matched: Turner’s Syndrome is a condition that affects only females, resulting when one of the X chromosomes (sex chromosomes) is missing or partially missing (45, X instead of 46, XX).
- Pair 3 is incorrectly matched: Klinefelter’s Syndrome is not caused by a deletion. It is caused by an extra X chromosome in a male (47, XXY). This results in a male who may have reduced muscle mass, facial hair, and body hair.
- Pair 4 is correctly matched: Cri-du-chat Syndrome (French for cry of the cat) is a rare genetic disorder caused by a deletion of genetic material on the small arm (p arm) of chromosome 5. Infants with this condition often have a high-pitched cry that sounds like that of a cat.
