Galactosemia (inability to metabolize milk sugar) is inherited as an autosomal recessive trait.

Galactosemia (inability to metabolize milk sugar) is inherited as an autosomal recessive trait. What is the probability of having sick children in a family where one of the spouses is homozygous for the galactosemia gene, but the development of the disease is prevented by diet, and the second is able to assimilate milk sugar, but heterozygous for the galactosemia gene?

Let’s write down the gene that causes galactosemia with the letter “a”, then the gene that causes the absence of the disease will be designated as “A”.

According to the condition of the problem, one of the spouses has galactosemia, which he managed to correct with a diet – aa. It produces the same type of sex cells a.

The second spouse is healthy and heterozygous for galactosemia — Aa. His body produces sex cells – A and a.

The couple has the following offspring options:

healthy children (Aa) – 50%;

children suffering from galactosemia (aa) – 50%.

Answer: the probability of giving birth to children with galactosemia in this couple is 50%.