Question

A $10$ year old patient is found to have the following clinical features: slanting eyes with epicanthic fold of skin in the eyelid, hypertelorism, dysplastic ears, mongoloid face and protruding tongue.
Which one of the following is the correct chromosomal complement of the above syndrome?
(A) $47$ Chromosomes due to extra chromosome $21$
(B)) $47$ chromosomes with $44A\,plus\,XXY$
(C) $45$ Chromosomes with $44A\,plus\,XO$
(D) Partial deletion of short arm of $5$ the chromosome

Answer 1

Hint: Trisomy $21$ is defined as the genetic disorder that occurs in the children due to the presence of one extra chromosome in the pair of $21$chromosomes. It is also known as Down syndrome, autosomal trisomy and autosomal aneuploidy.

Complete step by step answer:
Trisomy $21$ :
This disease is caused by the presence of $47$ chromosome due to the one extra chromosome that is three copies of chromosome $21$ instead of two pairs.

Symptoms:
It includes delaying of physical growth, slanting eyes in the flat head, hypertelorism, mangoloid face, protruding tongue, folded skin in the eyelids, irregularly shaped ears, very small head, ligaments are loose in nature, short neck and the white pigments in the iris of the human eye.
Hence the correct complement of chromosomes for the above syndrome is $47$ chromosomes due to extra chromosomes $21$.

So, the correct answer is “Option A”.

Note:
This disease occurs in the child of $8 - 10$ years old. This is mainly caused by the unusual or irregular cell division that occurs in the male or female gametes at the time of development of sperm or egg cell. This affects the brain and the body development of the baby that is developed from that irregular gametes.