Question

“Phenylketonuria is a good example that explains Pleiotropy”. Justify.

Answer 1

Hint: This is a disorder caused by a mutation in the gene. In this, a single gene can exhibit multiple phenotype expressions.

Complete step by step answer:
Pleiotropy is the phenomenon in which the single gene has multiple effects on a phenotype. The common example of pleiotropy is phenylketonuria.
Phenylketonuria is an inborn error of metabolism. This is also inherited as the autosomal recessive trait.
This single gene can control the various chemical reactions involved in the metabolism of phenylalanine. Mutation in the gene can result in phenylketonuria (PKU).

Additional information: Inheritance of phenylketonuria- For a child having Phenylketonuria, both the mother and father must have and pass on the defective gene. This pattern of inheritance is called autosomal recessive.
If only one parent has the defective gene, then there is no risk of passing phenylketonuria to a child, but it is possible for a child to be a carrier. Most often, this disorder is passed to children by two parents who are carriers of the disorder.
People affected with this lack of a liver enzyme called phenylalanine hydroxylase that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is accumulated and converted into phenyl pyruvic acid and other derivatives.
So, due to the accumulation of this phenylalanine in the brain results in mental retardation, idiots. This is also excreted through urine because of its poor absorption by the kidney.
The other symptoms are fair skin and blue eyes because phenylalanine can’t transform into melanin, this is the pigment responsible for hair and skin tone; abnormally small head; eczema; delayed growth, intellectual disability, microcephaly that is a small head, and some neurological problems.

Note:
- Phenylketonuria is associated with the autosomal gene, Chromosome 12.
- Disease could be avoided in the progeny by analyzing the pedigree of the parents.