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Polygenes and their inheritance pattern.pptx
- 1. Dr. Sandeep KumarRaghuvanshi Department of Zoology Bareilly College, Bareilly
- 2. •Polygene is whena 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
- 4. =*=--• ------A •• 1 __I ^ in pigmentation in human
- 5.
- 6. Though melanin productionis 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 aBab 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'd1d1D1 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 inWheat 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 AaBBAaBb 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 ABAb 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 PolygenicInheritance 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.
- 13.