Thalassemia is inherited as an incompletely dominant autosomal trait. In homozygotes, the disease is fatal in 90-955 cases. In heterozygotes, it is mild. What is the probability of having healthy children in a family where both parents suffer from a mild form of thalassemia?
Let’s designate the gene responsible for the development of thalassemia by the letter “A”, then the gene responsible for the synthesis of normal red blood cells will be “a”.
The fatal form of the disease, according to the condition of the problem, will develop in people homozygous for the dominant gene – AA.
A mild form of the disease will develop in heterozygotes, which are both parents from the condition of the problem – Aa. They produce sperm and eggs: A and a.
For this pair, the following offspring options are possible:
absolutely healthy children (AA) – 25%;
children with mild thalassemia – 50%;
children with lethal thalassemia 0 25%.
Answer: the probability of having healthy children for this couple is 25%.
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