Polygenic Inheritance

Polygenic Inheritance:

Polygenic inheritance is controlled by two or more pairs of nonallelic genes. In which the dominant alleles have a cumulative effect. Each dominant gene added will add to the character and the result will be an additive effect of all dominant genes. These genes are Polygenes and such type of inheritance is Polygenic inheritance. It is also referred as a Quantitative inheritance & Multiple genes interaction.

These genes don’t follow the Mendelian pattern of inheritance.

These characters are affected by environment.

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Continuous variation occurs. The offsprings can be divided into a range of classes.

  • Kolreuter first studied polygenic inheritance.
  • Galton studied it in man.
  • Nelson-Ehle gave the experimental proof.

Examples:

  • kernel color in wheat.
  • cob length in Maize.
  • skin color in man
  • height in man.
  • IQ in man.
  • crop yield, milk yield etc.

SKIN COLOR IN MAN: 

Studied by Davenport. 3 pairs of nonallelic genes are responsible for the character.

3 pairs of nonallelic genes are responsible for the character.

AABBCC   x    aabbcc

Negroes           Whites

                   ↓

AaBbCc  → F1 Generation

Mulattoes

FAaBbCc    x    FAaBbCc

The offsprings in F generation can be divided into a range of classes according to the number of dominant genes present.

 

KERNEL COLOR IN WHEAT:

2 pairs of nonallelic genes are responsible.

AABB    x     aabb

Red               white

              ↓

Medium color occurs in F1 generation.

when the Fis self-fertilised, F2 ratio is 1:4:6:4:1.

 

Mendelian inheritance is Monogenic inheritance.

These characters are controlled by 2 or more alleles of a gene and show discontinuous variation. It means the offspring are divided into 2 distinct classes.

It is Qualitative inheritance and environment has a lesser effect on these characters.

ALSO WATCH: Polygenic Inheritance

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