Question

12. List and briefly describe incomplete dominance, co-dominance, pleiotropy, and polygenic inheritance.

Answer 1

​​​​​​* Incomplete dominance: In this case, the one allele is incompletely dominant over the another allele. In heterozygous condition, there is found intermediate phenotype of both alleles.

For example: R gene encodes red color. It is incomplete dominant over r allele. r allele in homozygous recessive condition produces white color. In heterozygous (Rr) condition, the pink color is produced.

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* Codominance:In this case, one allele is codominant to the another allele. The heterozygous condition produces the expression of both alleles.

Example: R gene encodes red color. It is incomplete dominant over r allele. r allele in homozygous recessive condition produces white color. In heterozygous (Rr) condition, the white and red shading color is produced.

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*Pleiotropy: In this case, one gene encodes more than one phenotype.  

Example: Phenylketonuria: In this case, the gene is mutatef in such a way that phenylalanine hydroxylase enzyme is not produced. The nervous system, integumentary system is affected by this mutation.

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*Polygenic inheritance: In this case, more than one gene encodes a single trait.

Examples: The skin color is encoded by more than one genes.

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