Class 12 Biology Inheritance Variation MENDELIAN DISORDERS


  • Autosomal disorders – cystic fibrosis, sickle cell anaemia, myotonic dystrophy
  • Sex-linked – haemophilia, colour blindness
  • HAEMOPHILIA – sex-linked recessive disease
  • A single protein that is a part of the cascade of proteins involved in the clotting of blood is affected.
  • In affected individual, a simple cut will result in non-stop bleeding.
  • Heterozygous female (carrier) can transmit the disease to son.
  • Possibility of female becoming a haemophilic is extremely rare.


Pic shows cross between carrier haemophilic women and haemophilic man.

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