When one phenotypic expression is controlled by more than one gene, is known as polygenic inheritance. It is also called Quantitative inheritance. The quantity of inheritance depends on dominant alleles. Dominant alleles have a cumulative effect each expressing part of the trait. Gene involved in quantitative inheritance is known as polygenes. Polygenic inheritance doesn’t follow the Mendelian ratio. Eg; the skin color of humans, the height of humans, and wheat kernel color.

1. POLYGENIC
INHERITANCE
VIVA MARIYA K V
2ND DC BIOTECH
ST . MARY’S COLLEGE

2. POLYGENIC INHERITANCE
When one phenotypic expression is controlled by more than one gene, is
known as polygenic inheritance .
It is also called Quantitative inheritance.
The quantity of inheritance depends on dominant alleles.
Dominant alleles have cumulative effect each expressing part of trait.
Gene involved in quantitative inheritance is known as polygenes.
Polygenic inheritance don’t follow the mendelian ratio.
Eg; skin color of human , height of human and wheat kernel color.

3. SKIN COLOR OF MAN
 It was first studied by Devenport (1913) in case of Negro-Europeian
intermarriage.
 Skin color is due to pigment melanin . More pigment, darker is the
color.
 There are three gene controlling the production of melanin.
 But , for convenience we consider only two pair of genes.
 For Negro : AA BB CC ( maximum melanin)
 For Albino : aa bb cc (minimum melanin)

4. Negro
( high melanin)
AABBCC
Albino
(no melanin)
aabbcc
 Parents :-
Gametes:-
 F1
ABC abc
AaBbCc
Mulleto

5. F2:-
 when 3 polygene are
considered-
 When 2 polygene are considered- 1:4:6:4:1
ratio
PUNNETT SQUARE

6. Bar diagram of f2 generation in polygenic inheritance
PUNNETT SQUARE WITH NO.OF DOMINANT
ALLELES

7. THANK YOU