Question

Cri-du-chat syndrome in humans is caused by

• A. Trisomy of 21st chromosome
• B. Loss of half of short arm of chromosome 5
• C. Loss of half of long arm of chromosome 5
• D. Fertilization of an XX egg by a normal Y- bearing sperm.

Answer 1

The correct option is B Loss of half of short arm of chromosome 5

Trisomy of the 21 st chromosome causes Down's Syndrome (45+XY/45+XX). It is characterized by a round face, broad forehead and palmer crease with low intelligence. Fertilization of an XX egg by normal Y-bearing sperm results in 44+XXY chromosomes that causes Klinefelter Syndrome. The affected males are feminine and carry few feminine characters. Loss of half of the short arm of chromosome 5 causes Cri-du-chat Syndrome characterized by mewing like the cry of a newborn. Loss of half of the long arm of chromosome 5 causes a severe developmental delay in newborn.

The correct answer is option B.