What is sex-linked inheritance? Discuss how sex-linked gene inheritance occurs in human, giving two examples.

Explanation

Some genetic diseases are produced by the changes in genes lying in the sex-chromosomes. These are called sex-linked disorders. The transmission of sex-linked traits from parents to offspring is called sex-linked inheritance. The following are the sex-linked disorders which are caused by recessive gene located in the X-chromosome and affect the males more than the fernales.
These are as follows
Inheritance of Haemophilia le is a sex-linked recessive disease, which is transmitted from an unaffected carrier female to some of the male offsprings. Due to this, patient continues to bleed even during a minor injury because of defective blood coagulation and hence, it is also called as bleeders disease. The gene for haemophilia is located on X-chromosome and it is recessive to its normal ailele. In this disease, a single protein that is part of cascade of proteins involved in blood clotting is affected. The possibility of a female becoming a haemophilic is extremely rare because mother of such a female has to be atleast carrier and father should be haemophilic, e.g. females suffer from this disease only in homozygous condition, i.e. XX. The haemophilic alleles shows criss. Cross inheritance and they follow Mendelian pattern of inheritance.
Inheritance of Red-Green Colour Blindness it is a sex-linked recessive disorder, which results in defect in either red or green cone of eye. It does not mean the incapability to see any colour at all, Infact it leads to the failure in discrimination between red and green colour. The gene for colour blindness is present on X-chromosome
It is present mostly in males (X.Y) because of the presence of only one X-chromosome as compared to two chromosomes in females. A heterozygous female has normal vision, but is a carrier and passes on the disorder to some of her sons.