Everything you need to know

1. Prepared By: Richa Khatiwada

2. •Polygene is when a dominant allele controls only a unit or partial
quantitative expression of a trait.
•Several non-allelic genes affect same character.
•Also called multiple gene or quantitative or cumulative inheritance
as trait becomes more pronounced when dominant alleles are added.
•Each gene contributes equally.
•Environmental factors may also effect.
•Does not follow Mendelian ratio.
•Examples include skin color in human, kernel color on wheat,
human height, cob length in maize, etc.

3. History
Joseph Gottlieb Koleuter : Father of polygenic inheritance
Herman Nilsson-Elhe and East : First to discover polygenic
inheritance in kernel color in wheat
Charles B. Davenport and Gertrude C. Devenport :
Discovered that the inheritance of skin color in human occurs by
polygenic inheritance
J.B Koleuter C.B DavenportH Nilsson

4. Skin pigmentation in human

5. Trait Distribution

6. Though melanin production is regulated by 3 genes as above, for
convenience, we consider only two pairs of genes.
Parents
AABB
Negro
aabb
Albino
AB ab
AaBb
MullatoF1 generation
Gametes

7. F1
Gametes
AB Ab aB ab
AB AABB
Negro
AABb
Dark
AaBB
Dark
AaBb
Mulatto
Ab AABb
Dark
AAbb
Mulatto
AaBb
Mulatto
Aabb
Fair
aB AaBB
Dark
AaBb
Mulatto
aaBB
Mulatto
aaBb
Fair
ab AaBb
Mulatto
Aabb
Fair
aaBb
Fair
aabb
Albino
F2 generation phenotypic Ratio= 1: 4: 6: 4: 1
F2 generation

9. Kernel Color in Wheat

10. F2 generation phenotypic Ratio=1:4:6:4:1

11. Human Eye Color

12. Monogenic v/s Polygenic Inheritance
Monogenic Inheritance Polygenic Inheritance
Discontinuous variation Continuous variation
Single allelic gene Many non-allelic genes
Qualitative inheritance Quantitative inheritance
F1 individual resembles
dominant parent
F1 individual are intermediate
between the parents
Phenotype not influenced by
environment
Phenotype influenced by
environment
No intermediates Numerous intermediates
Eg: All seven characters studied
by Mendel
Eg: Skin color in human, Wheat
kernel color, etc.