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Cri-du-chat syndrome in humans is caused by the -
A
Fertilization of an XX egg by a normal Y-bearing sperm
B
Loss of half of the short arm of chromosome 5
C
Loss of half of the long arm of chromosome 5
D
Trisomy of 21st chromosome
Detailed Solution
Cri-du-chat (cat-cry) syndrome is a chromosomal disorder caused by a structural change, a deletion, and not by a change in chromosome number.
It is caused by the loss (deletion) of a part of the short arm (p arm) of chromosome 5; it is written as 5p-.
The affected baby has a characteristic high-pitched cry like the mewing of a cat, a small head (microcephaly), widely spaced eyes and severe mental retardation.
Fertilisation of an XX egg by a Y-bearing sperm gives XXY, which is Klinefelter's syndrome.
Trisomy of the 21st chromosome is Down's syndrome.
The deletion is in the short arm, not the long arm, of chromosome 5.
So cri-du-chat syndrome is caused by the loss of half of the short arm of chromosome 5.
It is caused by the loss (deletion) of a part of the short arm (p arm) of chromosome 5; it is written as 5p-.
The affected baby has a characteristic high-pitched cry like the mewing of a cat, a small head (microcephaly), widely spaced eyes and severe mental retardation.
Fertilisation of an XX egg by a Y-bearing sperm gives XXY, which is Klinefelter's syndrome.
Trisomy of the 21st chromosome is Down's syndrome.
The deletion is in the short arm, not the long arm, of chromosome 5.
So cri-du-chat syndrome is caused by the loss of half of the short arm of chromosome 5.