Question

Фенилкетонурия (нарушение аминокислотного обмена) наследуется как рецессивный признак. Жена гетерозиготна по гену фенилкетонурии, а муж гомозиготен по нормальному аллелю этого гена. Какова вероятность рождения у них больного ребенка?

Answer 1

Phenylketonuria (PKU) and Inheritance

Phenylketonuria (PKU) is an inherited metabolic disorder that affects the way the body processes the amino acid phenylalanine. It is inherited as a recessive trait, meaning that both copies of the gene responsible for PKU must be mutated for an individual to have the condition.

In this case, the wife is heterozygous for the PKU gene, meaning she carries one normal allele and one mutated allele. The husband, on the other hand, is homozygous for the normal allele, meaning he does not carry any mutated copies of the gene.

Probability of Having an Affected Child

To determine the probability of the couple having an affected child, we need to consider the possible combinations of alleles that can be passed on from each parent.

The wife can pass on either her normal allele or her mutated allele, while the husband can only pass on his normal allele.

There are four possible combinations of alleles that can be inherited by the child:

1. The child inherits the normal allele from both parents: This would result in a child without PKU. 2. The child inherits the mutated allele from the wife and the normal allele from the husband: This would result in a child who is a carrier of PKU but does not have the condition. 3. The child inherits the normal allele from the wife and the mutated allele from the husband: This would result in a child who is a carrier of PKU but does not have the condition. 4. The child inherits the mutated allele from both parents: This would result in a child with PKU.

Since the wife is heterozygous for the PKU gene, there is a 50% chance that she will pass on the mutated allele to the child. However, since the husband is homozygous for the normal allele, there is a 0% chance that he will pass on the mutated allele.

Therefore, the probability of the couple having a child with PKU is 0%.

Please note that this calculation assumes that the inheritance of the PKU gene follows simple Mendelian genetics and that there are no other factors or genetic modifiers involved. It is always recommended to consult with a genetic counselor or healthcare professional for a more accurate assessment of the risk of having an affected child.