Question
- Explain Polygenic inheritance and Multiple allelism with the help of suitable examples.
- "Phenylketonuria is a good example that explains Pleiotropy." Justify.
✓
Answer
- Traits that are generally controlled by three or more genes , the phenotype reflects the contribution of each allele/effect of each allele is additive
eg. Human skin colour, controlled by three genes (A , B, C)
In multiple allelism more than two alleles , govern the same character/phenotype eg . Human blood group (ABO system) , controlled by three different alleles (IA , IB, i)
- In pleiotropy a single gene can exhibit multiple phenotypic expressions , in phenyl ketonuria single mutated gene express mental retardation and reduction in hair and skin pigmentation.
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