Principles of Inheritance and Variation


  • A gene controlling more than 2 characters is called pleiotropism.
  • A gene in a pea plant is responsible for (i) red spot in leaf, (ii) Flower colour and (iii) Seed coat colour.
  • In human, HbS gene which differs from Hb+ gene in chr – 11, is responsible for (i) Haemolytic anaemia, (ii) increased resistance to one type of malaria caused by P. falciparum (iii) Development of tissues / organs.
  • In sickle cell anaemia (SCA), the 6th amino acid of the β chain, glutamic acid (glu) is replaced by valine (val)
  • Cystic Fibrosis (mutation in chr – 7) is also an example of pleiotropism.

Watch this video for the topic from 19:02 to 23:55

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