Polygenic traits and their inheritance:-

1) It is also known as quantitative or multiple factor inheritance.

2) When the expressed characters are totally distinct and easily separable they are termed as qualitative traits.

3) The traits in which the differences exist in degree only are quantitative traits.

4) The qualitative heritable traits phenotypic classes have always been distinct and easily separable from each other that is they have been sharply discontinuous, whereas quantitative characters are in continuous fashion.

5) Continuous variation is due to additive effect of two or more genes for a trait. Such a trait is also called as polygenic trait and the type of inheritance as multiple factor or polygenic inheritance.

6) It can be explained by taking an example of skin colour in human which is dependent upon relative amount of pigment melanin.

7) Davenport (1910) has shown that it is polygenic effect and is due to at least three separate genes.

8) They reported the results of studies regarding inheritance of skin colour in mullatoes i.e. population derived from marriages between Negros and white.

9) When F1 generation was obtained it was intermediate colours and population from such individuals different colour shades were obtained. Total 64 combinations were obtained.

10)    The ratio obtained was 1: 6: 15: 20: 15: 6: 1 for very dark, dark, fairly dark, intermediate, fairly light, light, white respectively.

11)    The other examples of ear size in maize, kernel colour in wheat, etc.

 

Phenotypic ratio in wheat kernel color:-