Principles of Inheritance and Variation
- The Two types of inheritance are monogenic (Qualitative) and polygenic (Quantitative) Inheritance.
- In monogenic inheritance, a single dominant gene influences a complete trait, that produces a discontinuous variation in trait expression.
- Polygenic inheritance is controlled by 3 or more genes, where dominant allele has cumulative effect with each dominant allele expressing a trait. Such genes are polygenes.
- Such type of inheritance is a.k.a multiple factor inheritance.
- Kolreuter first studied polygenic inheritance in tobacco height.
- Nilsson – Ehle got the first experimental proof of polygenic inheritance in kernel colour of wheat.
- In polygenic inheritance, the environment has greater effect on phenotypic expression.
- Davenport, first studied human skin colour in case of Negro – caucasian intermarriages in muda and Jamaica and found that the melanin quantity is controlled by 3 pairs of polygenes (A, B and C)
Watch this video for the topic from 23:57 to 37:24
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