Principles of Inheritance and Variation
Sex linked inheritance in humans
- If body characters are located by certain genes in X chromosomes, it is referred to as X linkage and if the genes for body characters are located in Y chromosomes then it is Y linkage.
- Certain X linked characters are Haemophilia (bleeders disease); colour blindness, night blindness etc.
- Y character linkage are associated only with males such as Hypertrichosis.
- X linkage was first observed in eye colour of drosophila.
- If the characters in a family donot shift in sexes then the inheritance is non-criss cross inheritance.
Eg : Hologenic inheritance (mother → daughter → grand daughter)
Holandric inheritance (Father → son → grandson) - In criss cross inheritance, the characters shift in sexes
Eg : Diagenic (Father → daughter → grand son)
Diandric (mother → son → grand daughter) - Baldness is a sex influenced character as it is differently influenced in both sexes. [ Eg. ‘Bb’ couses baldness in males, but not in Femals]
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