Principles of One-Gene Inheritance

  • The study and analysis of inheritance as a result of monohybrid crosses is called one-gene inheritance.
  • The cross between true-breeding pea plants with tall stems and dwarf stems is represent Mendel’s monohybrid crosses.
  • When Mendel crossed true breeding tall plants with dwarf plants, the resulting F1 generation consisted of only tall plants.
  • When members of the F1 generation were selfed cross, Mendel observed that 787 0f 1064 F2 plants were tall while 277 of 1064 were dwarf – a ratio of about 3:1.
  • Mendel made similar crosses between pea plants, exhibiting each of the other pairs of contrasting traits. In every case, the outcome was similar to the tall/dwarf cross.
  • Mendel proposed the existence of what he called ‘unit factors’ for each trait. He suggested that these factors serve as the basic unit of heredity and are passed unchanged from generation to generation.
  • Using the results of monohybrid crosses, Mendel derived the following three postulates, also known as ‘Principles of Inheritance’:
  1. Principle of paired factor:- Genetic characters are controlled by unit factors that exist in pairs in individual organisms.
  2. Principle of Dominance:- Out of the two contrasting traits, only one is able to express its effect in the individual. It is called dominant factor while the other is called recessive factor which does not show its effect.
  3. Principle of Segregation:- During the formation of gametes, the paired unit factors separate or segregate randomly so that each gamete receives one or the other with equal possibility.


mendel monohybrid cross

Published by

Shayan Ghani

The author is a co-founder and director at 'FLAIR - Innovative Classes for Maths and Science'. He is a post-graduate in Biotechnology from Patna University and currently living in Bihar (India).

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