Question

Describe the sex linked inheritance with the help of an example.

Answer 1

Sex Linked Inheritance

In humans there are 46 chromosomes (23 pairs): 22 pairs of autosomes and one pair of allosome (sex chromosomes). Men are heterogametic because they possess non-identical pair of sex chromosomes (one X chromosome and one Y chromosome), while women are homogametic (because they possess two identical X chromosomes). However, X chromosomes are much larger (than the Y chromosomes) and carry many more genes, and hence are more common than Y-linked traits.

The sex chromosomes not only determine the sex of the individual but also determine certain other characteristics that are also inherited. There are some genes located in the sex chromosomes that express non-sexual characters. Recessive characteristics from X chromosomes are expressed from all heterogametics, but they are expressed in homogametics only when they are homozygous for the recessive allele. Women mostly act as carriers of X-linked traits as the recessive allele in one is masked by the normal dominant allele in the other.

The genes located in different loci of the sex chromosomes exhibit patterns of inheritance that are related to sex. Genes that are present in X chromosome are called as sex linked genes or X-linked genes. Genes that are present in Y chromosome are called as holandric genes or Y-linked genes. The genes that are present in both X and Y chromosomes are known as incomplete sex linked genes.

Sex linked inheritance is called crisscross inheritance since the father passes the traits to the daughter, and she in turn passes the trait to the grandson. Examples of conditions that are inherited due to such inheritance are hemophilia and glucose-6-phosphate dehydrogenase deficiency.

hope it helps ♡♡