Colour-blindness: Understanding the X-linked inheritance of hereditary diseases

Date: May 20, 2015

Color blindness X linked inheritance Chromosomes

Colour-blindness: Understanding the X-linked inheritance of hereditary diseases

Colour-blindness is type of X-linked diseases which occur due to certain mutations present on X chromosomes. They are expressed when the both chromosomes are recessive for the same disease character. In males the gametes contain XY while females contain XX sets of chromosomes. Thus the diseases which are X-linked have females as carriers while males express the diseases.

Inheritance of X-linked gene for Colour-blindness in man:

The retina of the eyes of man contain colour sensitive cells which are necessary for distinction of red and green colours. These colour sensitive retinal cells are formed and are controlled by certain genes which are located on X-chromosome. The males having recessive genes of above mentioned genes remain unable to distinct the red and green colours.

Possibilities of inheritance of colour blindness:

  1. Marriage between Colour-blind man and normal visioned female: Such union will produce normal visioned males and females in F1 generation. The marriage between F1 normal visioned female and normal visioned female will produce F2 two normal visioned female, one normal visioned male and one Colour-blind male.

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  1. Marriage between normal visioned man and Colour-blind female (carrier): If a women (XX) is colour blind and she happens to marry normal visioned male (XY) then all F1 sons will be colour blind and daughters will be normal visioned.

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