Auricular hypertrichiasis is inherited as a hollandric trait, and albinism is an autosomal recessive trait

Auricular hypertrichiasis is inherited as a hollandric trait, and albinism is an autosomal recessive trait. In a family where the father had hypertrichiosis and normal pigmentation, and the mother was healthy, a girl with albinism was born. What is the probability of having an albino boy in this family?

The holandric trait means the fact that the gene that causes the development of hypertrichosis in humans is localized in the Y chromosome and is inherited in a state linked to it.

Let’s designate the chromosome, which includes the gene that causes the development of hypertrichosis, as Y g, then the chromosome with the gene that causes the absence of this pathology will be designated as Y.

Let’s designate the gene that determines the development of albinism as l, then the gene that determines the development of normal pigmentation of the skin and its appendages in humans will be designated as L.

A girl with albinism has the llXX genotype, because albinism appears only in people homozygous for the recessive gene that causes the development of this pathology. The girl inherited recessive genes from both parents, therefore, both the man and the woman for albinism are heterozygous carriers of the pathological gene – Ll.

The girl’s mother has the genotype LlXX and produces two types of oocytes – LX and lX.

The father of a girl with hypertrichosis has the genotype LlXY g. It produces four types of sperm – LY g, LX, lX, lY g.

The offspring of this married couple includes the following possible options:

boys with hypertrichosis (LLXY g, 2LlXY g) – 37.5%;

healthy girls (LLXX, 2 L lXX) – 37.5%;

girls with albinism (llXX) – 12.5%;

boys with albinism and hypertrichosis (llXY g) – 12.5%.

Answer: the probability of giving birth to a boy with albinism in this family is 12.5%, and simultaneously with albinism, the boy will have hypertrichosis.