Chapter 4 Study Guide

Question 1

1) A phenotype that is dominant in humans is a cleft chin. An unclefted chin is recessive. If a man with a cleft chin who is homozygous dominant has children with a woman with an unclefted chin, what are their chances of producing a child with an unclefted chin?
2) What are their chances of producing a child with a cleft chin?
3) What are the chances that their offspring will be heterozygous?

Answer 1

1) 0%
2) 100%
3) 100%

Question 2

1) Broad eyebrows are dominant over slender eyebrows. If 2 individuals, one homozygous for broad eyebrows and one heterozygous for broad eyebrows, have children, what are the chances that their children will have slender eyebrows?
2) What are the chances that their offspring will be carriers of the slender eyebrow trait?
3) Will any of their offspring have broad eyebrows?

Answer 2

1) 0%
2) 50%
3) Yes (all will)

Question 3

1) Farsightedness is dominant over normal vision. If a heterozygous farsighted man produces offspring with a woman with normal vision, what are the chances that their offspring will have normal vision?
2) What are the chances that their offspring will be farsighted?

Answer 3

1) 50%
2) 50%

Question 4

Straight hair is recessive while curly hair is dominant. If a woman with straight hair wants to have only offspring with curly hair, what are all the possible genotypes that the potential fathers may have?

Answer 4

Homozygous dominant

Question 5

Freckles are dominant over no freckles. A woman with freckles, but whose mother had no freckles, produces offspring with a man who is homozygous for freckles. What are the chances that they will produce offspring without freckles?

Answer 5

0% (50% heterozygous 50% homozygous dominant)

Question 6

1) Red hair is due to a recessive allele, non-red hair is dominant. If a woman’s second child has red hair, what is the genotype of the child’s father?
2) What is the genotype of the mother?

Answer 6

1) Heterozygous
2) Homozygous recessive

Question 7

1) Red hair is due to a recessive allele, non-red hair is dominant. If a woman’s second child has red hair, what is the genotype of the child’s father?
2) What is the genotype of the mother?

Answer 7

1) Heterozygous
2) Homozygous recessive

Question 8

1) Marfan’s syndrome is an inherited recessive disorder that affects connective tissue in the body, while the normal condition is dominant. If two parents, both heterozygous, produce offspring, what are the chances that they will produce a normal child?
2) What are the chances they will produce a child that is a carrier of Marfan’s?
3) What are the chances they will produce a child with Marfan’s?

Answer 8

1) 25% chance of normal genotype
2) 50% chance of heterozygosity
3) 25%

Question 9

1) Huntington’s disease is due to a dominant allele. If a man who is heterozygous for Huntington’s disease marries a normal woman, could any of their children have Huntington’s disease?
2) What is the chance any of their offspring will develop Huntington’s?

Answer 9

1) Yes
2) 50%

Question 10

1) Tongue folding is a recessive trait and the inability to fold the tongue is dominant. If two heterozygous parents have offspring, what is the chance their offspring will be able to fold their tongue?
2) What is the chance their child will be unable to fold their tongue?

Answer 10

1) 25%
2) 75%

Question 11

ABO blood group: If a mother is heterozygous for B and a father is type O, what would be the expected phenotypes of the children from this union? Include the percentages.

Question 12

ABO blood group: Two individuals are heterozygous for B. What would be the expected genotypes of their children? Include the percentages

Question 13

Show how a mother can have a child that is type O blood and a child with type AB blood. List all of the prospective genotypes the mother could have

Question 14

A couple has children and their offspring are all AB. For this couple to have offspring that are only able to have type AB blood, what are the genotypes of the parents?

Answer 14

****AB and AB

Question 15

1) A child has type B blood. His mother is type O. His brother is type A. What is the father’s genotype?
2) List all the phenotypes and percentages based on this union

Question 16

1) Red-green color blindness is due to an X-linked recessive trait. The normal condition is dominant. If a colorblind male has children with a normal woman but whose father was colorblind, what percentage of their male offspring will be colorblind?
2) What percent of their female offspring will be color blind?
3) What percent of their female offspring will be carriers of the color blind trait?

Answer 16

1) 50%
2) 50%
3) 50%

Question 17

1) Becker muscular dystrophy is due to an X-linked recessive trait. The normal condition is dominant. If a normal woman who is not a carrier marries a man with Becker dystrophy, what percent of their female offspring will have Becker dystrophy?
2) What are the phenotypes of the female offspring? What are the genotypes of the female offspring?
3) Will the male offspring have to worry about inheriting Becker dystrophy?
4) What are the genotypes of the male offspring?

Answer 17

1) 0%
2) All don’t have Becker dystrophy; 100% heterozygous
3) No
4) Homozygous dominant (normal)

Question 18

Sickle cell anemia is an example of incomplete dominance. Homozygous dominant is normal, heterozygous results in sickle cell trait, and homozygous recessive results in sickle cell anemia.
1) If two parents have sickle cell trait, what percent of the offspring will be normal?
2) What percent will have sickle cell trait?
3) What percent will have sickle cell anemia?

Answer 18

1) 25%
2) 50%
3) 25%

Question 19

Sickle cell anemia is an example of incomplete dominance. Homozygous dominant is normal, heterozygous results in sickle cell trait, and homozygous recessive results in sickle cell anemia.
1) If a woman with sickle cell anemia marries a normal man, what are the chances they will produce a normal child?
2) What percentage will have sickle cell trait?
3) What percentage will have sickle cell anemia?

Answer 19

1) 0%
2) 100%
3) 0%

Question 20

Hemophilia is due to an X-linked recessive strait. The normal condition is dominant.
1) If a woman with hemophilia has children with a normal male, what is the chance of hemophilia among their daughters?
2) What are their daughters genotypes?
3) What are their sons genotypes?

Answer 20

1) 0%
2) Heterozygous
3) All sons have hemophilia (recessive trait on X and normal Y)

Question 21

1) Hair on the hand is dominant over no hair on the back of the hand. Is it possible for two individuals with hair on the backs of their hands to have offspring who don’t have hair on the backs of their hands?
2) What would be the genotypes of the parents?

Answer 21

1) Yes
2) Heterozygous