Botany krishna series 2nd semester Only Mcq type questions
Polygenes and their inheritance pattern.pptx
1. Dr. Sandeep Kumar Raghuvanshi
Department of Zoology
Bareilly College, Bareilly
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. 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 p
J.B Koleuter H Nilsson C.B Davenport
6. Though melanin production is regulated by 3 genes as above, for
convenience, we consider only two pairs of genes.
AABB
Parents
Negro
aabb
Albino
Gametes AB ab
FI generati»n Mullato
7. Fi
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
8. Gene 1 d'd1 d1D1 d'D' D'D1 D’d1
D1d» D'D1
Gene 2 d2d2 d2d2 d2D2 D2d2 D2d2 D2D2
D2D2
Gene 3 d3d3 d3d3 d3d3 d3d3 D3D3 D3D3 D3D3
Total 0 1 2 3 4 5 6
numberof
dark-skin
genes
Medium Very
dark
# of light
“d" alleles
U of dark
UD’
alleles
5
1
9. Kernel Color in Wheat
aa bb cc x AA BB CC
(pure white line) (pure red line)
l
Aa Bb Cc (medium red)
Self-fertilization
aabbcc
AAbbcc AaBbcc
aaBBcc Aabbcc
AabbCc aaBbcc
aabbCC aabbCc
aaBbCc
AABbcc
AAbbCc AABBcc AaBBcc AABbCc
AabbCC AAbbCC aaBBCc AaBbCC
AABBCc aaBbCC aaBBCC AaBBCC
AaBbCc AaBBCc AABbCC AABBCC
0 1 2 3 4 5 6
Number of red pigment alleles (A, B or C) in genotype
10. AABb
DARK
AaBB
OARK
AaBt>
MEOIUM
AABB AABb AaBB AaBb
RED OARK DARK MEOIUM
AAbb AaBb Aabt
MEOIUM MEDIUM LIGHT
AaBb aaBB aaBb
MEOIUM MEOIUM LIGHT
Aabb aaBb aabb
LIGHT LIGHT WHITE
REO
AABB
1
WHITE
aabb
i
ab
Parents
Gametes ► AB
F* Generation MEOIU
M
AaBb
Gametes
F2 generation phenotypic Ratio=1:4:6:4:1
11. Mother
Human Eye Color
Father
AaBb
AB Ab aB ab
AB
•
AABB
•
AABb
•
AaBB
9
AaBb
Ab
•
AABb
#
A Abb AaBb
#
Aabb
aB
•
AaBB
m
AaBb
#
aaBB
•
aaBb
ab
#
AaBb
#
Aabb
#
aaBb
#
aabb
12. onogenic v/s Polygenic Inheritance
Monogenic Inheritance 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.