Question

The syndrome exhibiting trisomy in 21st chromosome is

• A. Cri du chat synfrome
• B. Turner's syndrome
• C. Klinefelter's syndrome
• D. Down syndrome

Answer 1

The correct option is D Down syndrome

Down syndrome is the genetic disorder caused by the nondisjunction of the chromosome where an individual carries one extra chromosome at chromosome 21 and hence called as trisomy 21. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This type of Down syndrome, which accounts for 95% of cases, is called trisomy 21. Trisomy in 21st chromosome does not cause turner's syndrome, cri du chat syndrome and Klinefelter's syndrome. Thus, option D is correct.