In Turner syndrome,a female has:

Given below are two statements :
Statement $I$ : Down's syndrome is caused by the absence of one of the $X$-chromosomes.
Statement $II$ : Turner's syndrome is caused by the presence of an additional copy of the chromosomes.
In the light of the above statements, choose the correct answer from the options given below :

- Physical, psychomotor and mental development is retarded.
- Palm is broad with characteristic palm crease, these symptoms show....

Distinguish between: Down's syndrome and Klinefelter's syndrome.

$A$ person having $45$ chromosomes where the $Y$ chromosome is absent. Such a condition is known as

Turner's syndrome in humans is caused by