Question

Which one of the following statements is wrong?

• A. Down’s syndrome is caused due to the non‐disjunction of chromosomes during meiosis.
• B. Klinefelter’s syndrome is an example for autosomal hyper‐aneuloidy.
• C. The individuals with Turner’s syndrome will have 45 chromosomes in each of the diploid cells.
• D. Cri du chat syndrome occurs due to the partial deletion of short arm of 5th chromosome.

Answer 1

Answer: (B)

Klinefelter's syndrome, or syndrome is a condition in which human males have an extra X chromosome. Hence it can be called as a sex chromosomal disorder. Down syndrome or Down's syndrome, (also known as trisomy ), is a chromosomal condition caused by the presence of all or part of an extra chromosome ( or ). Down’s syndrome is caused by a meiotic non‐ disjunction event. With non‐disjunction (non‐separation), a gamete (i.e., a sperm or egg cell) is produced with an extra copy of chromosome ; the gamete thus has chromosomes. When combined with a normal gamete from the other parent, the embryo now has chromosomes, with three copies of chromosome . Turner syndrome , is seen in human females, of which monosomy (absence of an entire sex chromosome, ie., chromosome) is most common. Cri du chat syndrome is a rare genetic disorder due to a missing part of chromosome . Cri du chat syndrome refers to the characteristic cat‐like cry of affected children.