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InterviewSolution
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(a) How are Mendelian inheritance, polygenic inheritance arid pleiotropy different from each other ? (b) Explain polygenic inheritance pattern with the help of a suitable example. |
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Answer» Pleiotropy-A single gene that has an effect on the expression of two or more phenotypic traits is said to have a pleiotropic effect- on the traits. For example, testosterone controls the development of what are referredto as secondary sexual characteristics, but testosterone also relates to behavioral traits like aggression. Thus, a gene that controls the level of testosterone would have a pleiotropic effect on the expression of many secondary sexual traits which are morphological, as well as behavioral 2. Polygenic Iftwo or more genes are responsible for a single trait, the phenotypic trait is said to be governed by polygenic factors. For example, growth rate is undoubtedly caused by a number of genes that act in a complex cascade. 3. Mendelian inheritcance : It states the following : (a) Law of Dominance (i) Characters are controlled by discrete units called factors. (ii) Factors occur in pairs. (iii) In a dissimilar pair of factors one member of the pair dominates (dominant) the other (recessive). (b) Law of segregation:Aeles do not show any blending and both the charactors are recovered in `F_2` generation though one of these is not seen at the `F_1` stage. (c) Law of independent assortment: When two pairs of traits are combined in a hyhrid, segregation of one pair of characters is independent of the other pair of characters. (b) See point 2., Polygenic inheritance [above]. . |
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