A color-blind man marries a homozygous normal woman, and after several years they have two children....

A color-blind man marries a homozygous normal woman, and after several years they have two children. Unfortunately, both children have Turner syndrome, although one has normal vision and one is color-blind. The type of color blindness involved is sex-linked recessive trait.

a.) Write the genotype of a person with Turner’s syndrome?

b.) For the color-blind child did nondisjunction occur in the mother or the father? Explain your answer.

c.) For the child with normal vision in which parent did nondisjunction occur? Explain your answer.

2) A genetic disorder caused by an autosomal, recessive allele is characterized by falling asleep in genetics lectures when the lectures begin at 8 a.m. It is also characterized by waking up as the lecture ends. The disease is known to be 80% penetrant. Complete expressivity occurs in only 20% of people that exhibit the disorder. Incomplete expression occurs only when the person falls asleep, but fails to wake up as the lecture ends.

a) Must the percentages of penetrance and expressivity sum to 100%?

b) What percentage of students who are homozygous for the recessive allele will both fall asleep at 8:00 a.m. and still be sleeping when the lecture ends?

Expert Solution

Genotype of father XcY and of mother is XX. This genotype is decide according to question which says that father is color blind(x linked recessive) mother is homozygous normal.

Both the children are having Turner's syndrome. This is a syndrome in which females have only one X chromosome in place of 2 X chromosomes. It means both children are female. One of them is color blind while other is normal.

a. Genotype with Turner's syndrome is XO

b. The genotype of colorblind child would be XcO. In this case, the X chromosome is definitely inherited from father. It means non disjunction occurs in mother. So no X chromosome is inherited from mother.

c. The genotype of normal child would be XO. In this case, the X chromosome is definitely from mother. It neans non disjunction occurs in father. So no X chromosome is inherited from father.

gladiator answered 2 years ago

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