Question

Which is due to the $4^{th}$ chromosomal abnormality?
A. Huntington Chorea
B. Cri-du-Chat or Cat-cry syndrome
C. Achondroplasia
D. Both A and C

Answer 1

A chromosomal abnormality can be of numbers or build up(structural). Numerical abnormality means missing one of the chromosomes from a pair or in cases where there are more than two chromosomes. A structural chromosome means its structure is altered in one of several ways.

Complete answer:
Now let us discuss all the above abnormalities one by one.
(1) Huntington Chorea: This disease is caused by an inherited defect in a single gene. In this case if a person gets one copy of the defective gene it will lead to disorder. This is a brain disorder caused by a single defective gene on the $4^{th}$ chromosome.
(2) Cri-du-Chat or Cat-cry syndrome: This is one of the syndromes which is a very rare genetic condition that is caused by missing pieces of genetic material on P arm of the chromosome which is also known as the small arm.
(3) Achondroplasia: In such disorders there is bone defect. That means dwarfism. Dwarfism can be defined as a condition of short height in adults with abnormal size. It is caused by mutation in the FGFR3 gene causing protein to be more active.

Hence, the correct answer is option (A)

Note: Chromosome four is more likely to have 1,000 to 1,100 genes that give instructions for making proteins. These proteins perform various jobs in the body. Proteins are very important for human growth.