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]

Part-1: Watch this video for the topic from 0:13 to 12:42

Part-2: Watch this video for the topic from 0:10 to 5:25

Part-3: Watch this video for the topic from 0:10 to 14:21

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