Question

The gene disorder phenylketonuria is an example for
A. Polygenic inheritance.
B. Pleiotropy
C. Multiple allelism.
D. Multiple factor.

Answer 1

Hint: Phenylketonuria (PKU) is a metabolic disorder in which the amino acid phenylalanine is not properly metabolized. PKU can cause intellectual handicap, seizures, behavioral issues, and psychiatric illnesses if left untreated. It could also cause a musty odor and lighter skin. Heart issues, a small head, and low birth weight are all possible outcomes for a baby born to a woman with inadequately treated PKU.

Complete answer :
Option A Polygenic inheritance : In simple words, polygenic inheritance refers to a character or phenotypic characteristic that is controlled by multiple genes. It is a type of quantitative inheritance in which two or more separate genes influence a single phenotypic feature in an additive manner. Phenylketonuria is not an example of polygenic inheritance. Hence option A is not correct.
Option B Pleiotropy : Pleiotropy arises when one gene influences two or more phenotypic qualities that appear to be unrelated. Phenylketonuria (PKU) is one of the most well-known examples of pleiotropy in humans. A lack of the enzyme phenylalanine hydroxylase, which is required to convert the essential amino acid phenylalanine to tyrosine, causes this condition. Hence option B is the correct answer.
Option C Multiple allelism : Multiple allelism is defined as the presence of three or more alleles of a gene. One of the best examples of multiple allelism is the ABO blood group system. Phenylketonuria is not caused by multiple allelism. Hence option C is not correct.
Option D Multiple factor : Multiple gene inheritance or multiple factor inheritance are other terms for polygenic inheritance. Quantitative inheritance is defined as when numerous independent genes have a similar or additive effect on a single quantitative trait. Phenylketonuria is not an example of multiple factor inheritance. Hence option D is not correct.

Therefore, option B. Pleiotropy is the correct answer

Note :
Phenylketonuria is a hereditary condition that is passed down through the generations. It's caused by mutations in the PAH gene, which cause phenylalanine hydroxylase levels to drop. As a result, dietary phenylalanine levels rise to potentially lethal levels. It is autosomal recessive, which means that for the disorder to manifest, both copies of the gene must be altered.