Given the following information, explain how we can we say that \"PKU is a genet

Question

Given the following information, explain how we can we say that "PKU is a genetic condition under strong environmental influence" when the environment does not influence the expression of the allele (gene) underlying this condition...

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Many times in class we said that P = G x E.

And yet, what we mean by "environmental effects" is often slightly misunderstood.

Phenolketonuria (PKU) is a recessive condition that can cause brain damage in affected children. But if PKU-affected children are placed on a phenylalanine-low diet, they do fine. For this reason, we say that PKU is a condition (phenotype) that is under strong environmental influence or effect (in this case the environmental factor is the diet, of course).

However, using molecular biology techniques, we can see that the enzyme that causes PKU is expressed at the same levels in children on a normal or Phenylalanine-low diet. So, how can we say that "PKU is a genetic condition under strong environmental influence" when the environment does not influence the expression of the allele (gene) underlying this condition...?

Explain in 100 words or fewer. Top submissions, extra points.

Explanation / Answer

"Phenyl ketonuria is a genetic condition under strong environmental influence". The present statement is highy true as the PKU genetic condition is caused by a genetic condition and influenced or let us say controlled by environmental influence i.e. diet. Individuals who are homozygous for the PKU gene have a deficiency in the enzyme required to convert phenylalanine to tyrosine. If left untreated, a buildup of blood phenylalanine occurs after birth (before birth, the mother’s enzymes are used), and the high blood phenylalanine levels cause mental retardation. The retardation can be prevented if blood phenylalanine levels are kept low by dietary restriction.

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