Cri-du-chat syndrome in humans is caused by the-
- Loss of half of the long arm of chromosome 5
- Loss of half of the short arm of chromosome 5
- Trisomy of 21st chromosome
- Fertilization of an XX egg by a normal Y-bearing sperm
Answer
(2) Loss of half of the short arm of chromosome 5
Solution
∵ Cri-du-chat (cat's cry) syndrome is a chromosomal disorder caused by deletion of a part of the short arm (p arm) of chromosome 5 (5p-).
⇒ Affected infants have a cat-like cry, microcephaly and mental retardation.
⇒ Trisomy of chromosome 21 causes Down's syndrome, and an XX egg fertilised by a Y-bearing sperm (XXY) gives Klinefelter's syndrome.
∴ Cri-du-chat syndrome is caused by loss of half of the short arm of chromosome 5.
Answer: (2)