One form of anemia is inherited as an autosomal dominant trait. In homozygotes, this disease leads to death

One form of anemia is inherited as an autosomal dominant trait. In homozygotes, this disease leads to death, in heterozygotes it manifests itself in a mild form. A woman with normal vision and a mild form of anemia gave birth to a color-blind man who was healthy in blood, a son suffering from a mild form of anemia and color blindness. Determine the probability of the birth of the next son without anomalies, indicating his genotype?

Let’s designate the gene that determines the development of anemia as K, then the gene that determines the well-being of human health in relation to this disease will be designated as k.

Only patients heterozygous for the genotype are viable with this anemia – Kk.

As you know, the gene for color blindness is inherited in the X – chromosome, let’s designate it as X d. Then the chromosome with the gene for normal color discrimination will be X D.

A son born with both pathologies has the KkX dY genotype. Since he inherits the Y chromosome from his father, which determines his development according to the male type, this child inherits the X d chromosome with the pathological gene for color blindness from his mother. Since the mother normally identifies colors, her genotype is heterozygous and looks like this – Kk X D X d. This woman is capable of producing four types of eggs – KX D, k X d, K X d, k X D.

A man with color blindness, not suffering from anemia, has the kkX d Y genotype and produces two types of spermatozoa – kX d, kY.

The offspring of this married couple are represented by the following possible options:

girls with mild anemia (KkX D X d) – 12.5%;

girls with color blindness (kk X dX d) – 12.5%;

girls with mild anemia and color blindness (Kk X dX d) – 12.5%;

healthy girls (kk X D X d) – 12.5%;

boys with mild anemia (KkX D Y) – 12.5%;

boys with color blindness (kk Xd Y) – 12.5%;

boys with mild anemia and color blindness (Kk X d Y) – 12.5%;

healthy boys (kk X D Y) – 12.5%.

Answer: This married couple has a 12.5% ​​chance of having a healthy son. Its genotype, according to the introduced conventions, is kk X D Y.