11) Cystic fibrosis (CF) is caused by a recessive allele. A child has CF, even though neither of his parents has CF. Which of the following describes the genotypes of the parents?

A) One is homozygous dominant for the CF gene, and the other is heterozygous.

B) One is homozygous recessive for the CF gene, and the other is heterozygous.

C) They are both homozygous recessive for the CF gene.

D) They are both homozygous dominant for the CF gene.

E) They are both heterozygous for the CF gene.

12) Cystic fibrosis (CF) is caused by a recessive allele. A child has CF, even though neither of his parents has CF. This couple also has a child who does not have CF. What is the probability the unaffected child is heterozygous?

A) 2/3

B) 1/3

C) 1/2

D) 3/4

E) 1/4

13) When a yellow-seeded pea plant with the genotype Yy produces gametes, what will be the genotype(s) of the gametes?

A) All will be YY.

B) All will be Yy.

C) They will be either all Y or all y.

D) Half will be YY, and half will be yy.

E) Half will be Y, and half will be y.

14) In Mendel’s pea plant experiments, in order for him to have observed a 3:1 phenotypic ratio in the F2 generation, which of the following must be true?

A) The two alleles of a pair separate in gamete formation.

B) The pairs of alleles must be either homozygous dominant or homozygous recessive.

C) Both alleles of a pair must go into each gamete together.

D) Both of the F1 parents must be breed true.

15) The genotype Ff is an example of a:

A) trait controlled by multiple genes.

B) homozygous genotype.

C) monohybrid genotype.

D) heterozygous genotype.

E) dihybrid genotype.

16) Widow’s-peak hairline in humans is dominant to non-widow’s-peak hairline. If a person has a widow’s-peak hairline, what is his or her genotype?

A) The genotype must be homozygous recessive.

B) The genotype is either homozygous dominant or homozygous recessive.

C) The genotype must be heterozygous.

D) The genotype is either heterozygous or homozygous dominant.

E) The genotype must be homozygous dominant.

17) The Law of Segregation states that:

A) gene pairs assort independently of each other during gamete formation.

B) differing characters in organisms result from two alleles that separate in gamete formation, such that each gamete gets only one of the two alleles.

C) differing characters are the result of either the homozygous dominant or the homozygous recessive condition.

D) phenotypes are always determined by genotypes.

E) one allele of a pair must always be dominant and the other must always be recessive.

18) If an individual exhibits a recessive trait, which of the following statements can you be sure of?

A) The phenotype for this trait is different from the phenotype of the homozygous dominant genotype for this trait.

B) The genotype of this trait will be heterozygous.

C) Both parents of this individual had the same genotype for this trait.

D) Any siblings of this individual will have the same phenotype for this trait.

E) Any children this individual has will always exhibit the trait, regardless of the genotype of the other parent.

19) Dimpled cheeks are dominant to undimpled cheeks. If there exists a 50 percent chance that a child will have dimpled cheeks, the parental genotypes must be:

A) dd and dd.

B) Dd and dd.

C) DD and Dd.

D) Dd and Dd.

E) DD and dd.

20) When two identical alleles for a character are present, the genotype is referred to as:

A) heterozygous.

B) homozygous.

C) dominant.

D) recessive.