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

The "cri-du-chat" syndrome is caused by a change in chromosome structure involving:

In humans,sometimes during gametogenesis,sex chromosomes do not separate,resulting in a chromosome number of $45$,$47$,or $48$. In this condition,which of the following genotype and phenotype combinations is correct?

What is the sex chromosome complement in a male child with Down syndrome?

What is Down's syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down's syndrome increase if the age of the mother exceeds forty years?

The movement of a gene from one linkage group to another is called