Explain the inheritance of sex linked recessive character in human being.

Explanation

The X-linked genes are represented twice In female (because female has two "R-chromosomes) and once . males. (because male has one X-chromosome). . male single X-linked recessive gene express it phenotypically, hi contrast to female hi which two IC • linked recessive genes are necessary for the determination of a single phenotypic trait related to sex.
The recessive X-linked genes have characteristic ,Crisscross .inheritance
Crisscross inheritance The inheritance of .,linked recessive trait (genes) to his grandson (`F_2`) through his daughter (carrier) is called crisscross inheritance. Crisscross Inheritance can be explained in humans by sex-linked recessive disorder, colour blindness.
Colourblindness: Colour blindness is a particular trait . human beings render them unable to differentiate between red and green colour. The gene for this colour blindness is located on X-chromosome. Colour blindness . recessive to normal vision so that if colour blind man marries a normal vision (homozygous) woman, all the sons acid daughters are normal but daughter are heterozygous, which means that these daughters would be carrier for this trait. If such carrier woman marries a man with normal vision all the daughters and half of the sons have normal vision and half of sons are colour blind:
Colour blind trait is inhereted from a male parent to his grandson through carrier daughtet i.e., trait shows crisscross inheritance.

Characteristics of X-linked recessive traits
They never passed from father to son. ,
Male are much more likely to be affected because they need only one copy of the mutant allele to express the phenotype.
Affected males get the disease from their carrier mother only.
Sons of heterozygous female carrier female) have 50% chance of receiving mutant alleles. These disorders are typically passed from an affected grandfather to 50% of his grandsons.
The X linked recessive traits shows Crisscross pattern of inheritance.
Eg: Colourblindness, Hemophilia,Muscular, dystrophy etc.