Question

The individuals suffering from which of the following syndromes have a normal sex chromosome complement?

• A. Klinefelter’s syndrome
• B. Turner’s syndrome
• C. Down’s syndrome
• D. Triple X syndrome

Answer 1

The correct option is C Down’s syndrome

Human beings have 46 chromosomes in all the cells except the gametes which have 23 chromosomes.

Out of this, 44 are autosomes and two are sex chromosomes.

X and Y are the sex chromosomes. Males have one X and one Y chromosome.
Females have two X chromosomes.

Down’s syndrome is an autosomal chromosomal disorder which is caused due to nondisjunction resulting in the presence of three copies of the 21st chromosome instead of two.

The affected individuals have 47 chromosomes, in which 45 autosomes are present instead of 44. But, they have normal sex chromosome complement.

Klinefelter’s syndrome is characterised by the presence of an extra X chromosome in males. They have 44 autosomes and 3 sex chromosomes (44 + XXY).

Turner’s syndrome is characterised by the absence of an X chromosome in a female. They have 44 autosomes and one sex chromosome (44 + XO).

Triple X syndrome is characterised by the presence of an extra X chromosome in females. They have 44 autosomes and 3 sex chromosomes (44 + XXX).