Biology Practice Problems Genetic Counseling Practice Problems Solution: In humans, dark hair (B) is dominant over blondnes...

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Solution: In humans, dark hair (B) is dominant over blondness (b), and color blindness (c) is a sex-linked recessive trait. A women has a blond brother, a blond mother, and a dark-haired father. Her brother and her parents have normal vision. She bears the following three children by her blond, normal-visioned husband:a dark-haired son with normal vision,a dark-haired daughter with normal vision, anda dark-haired color-blind soni) Make a pedigree of the entire family showing the probable genotypes of all individuals.ii) What is the probability that her next (fourth) child will be a color-blind boy?iii) If her fourth child is a boy, what is the probability that he will have dark hair?iv) What is the chance that her next four children will all be girls?

Problem

In humans, dark hair (B) is dominant over blondness (b), and color blindness (c) is a sex-linked recessive trait. A women has a blond brother, a blond mother, and a dark-haired father. Her brother and her parents have normal vision. She bears the following three children by her blond, normal-visioned husband:

a dark-haired son with normal vision,

a dark-haired daughter with normal vision, and

a dark-haired color-blind son

i) Make a pedigree of the entire family showing the probable genotypes of all individuals.

ii) What is the probability that her next (fourth) child will be a color-blind boy?

iii) If her fourth child is a boy, what is the probability that he will have dark hair?

iv) What is the chance that her next four children will all be girls?