Question

Cri-du-chat syndrome is due to chromosomal change involves
A) Duplication
B) Inversion
C) Deletion
D) Translocation

Answer 1

Hint: Chromosomal changes are caused due to either the change in shape or structure of the chromosome or the change in genetic information of the chromosome or change in number of chromosomes that ultimately leads to change in gene expression.

Complete answer
The four major types of change in chromosomal structure are-
i) Deletion
ii) Duplication
iii) Inversion
iv) Translocation

Deletion is a type of chromosomal change that leads to loss of a part of the chromosome or a sequence of the DNA. This leads to loss of genetic information. Deletion can range from loss of a single nucleotide or a single base to an entire chromosome.

Duplication is a chromosomal change where new genetic information is generated which may be due to recombination, replication slippage or retrotransposition. Inversion is a chromosomal change where a segment of chromosome is reversed end to end.

Most commonly an inversion occurs when a chromosome undergoes breakage and then rearranges within itself. Translocation is a chromosomal change where a region of the chromosome breaks and attaches to a different chromosome. Cri du chat syndrome is a chromosomal aberration where deletion of genetic information takes place on the small arm of chromosome 5.

Hence the correct answer is option (A) Deletion.

Note:The cri-du-chat syndrome is named after the characteristic cry of the affected infants which is caused due to the problems of the larynx and nervous system. Few symptoms include difficulty in swallowing, mutism, poor growth, behavioural problems and unusual facial features.