Question

In which of the following there is no defect in the sex chromosome?

• A. Turner's syndrome
• B. Down's syndrome
• C. Colour blindness
• D. Klinefelter's syndrome

Answer 1

Answer: (B)

Down's syndrome

Down's syndrome is a chromosomal disorder which is caused due to the trisomy of the 21${}^{st}$ chromosome. It is mainly caused by the nondisjunction of chromosomes during meiosis which produces an extra copy of chromosome 21. Distinctive facial features, such as a flat face, small ears, slanting eyes, and a small mouth, a short neck and short arms and legs, low muscle tone and loose joints are some common symptoms of the disease.