Question 1

Which of the following best describes Mendel's Law of Segregation?

Accepted Answer

Alleles for a trait separate during gamete formation, so each gamete carries only one allele for each gene.

Question 2

A monohybrid cross between two heterozygous pea plants (Yy x Yy) results in what phenotypic ratio in the F2 generation?

Accepted Answer

$$3:1$$

Question 3

Which of the following scenarios best illustrates Mendel's Law of Independent Assortment?

Accepted Answer

A dihybrid cross (RrYy x RrYy) produces offspring with new combinations of seed shape and color.

Question 4

In a test cross, an individual with an unknown genotype for a dominant trait is crossed with a homozygous recessive individual. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 5

A couple, both carriers for cystic fibrosis (a recessive disorder), want to know the probability that their child will have the disease. What is the probability?

Accepted Answer

$$\frac{1}{4}$$

Question 6

Which of the following is an example of polygenic inheritance?

Accepted Answer

Human height

Question 7

A woman who is heterozygous for the gene that causes sickle-cell disease (Ss) marries a man who is also heterozygous (Ss). What is the probability that their child will be a carrier but not have the disease?

Accepted Answer

$$\frac{1}{2}$$

Question 8

Which of the following statements about dominant and recessive alleles is correct?

Accepted Answer

A dominant allele will mask the expression of a recessive allele in a heterozygote.

Question 9

A pedigree shows a trait that appears in every generation and all affected individuals have at least one affected parent. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 10

Which of the following best explains why some genetic disorders, such as Huntington's disease, persist in the population despite being caused by dominant lethal alleles?

Accepted Answer

The disorder only affects individuals after reproductive age, allowing the allele to be passed on.

Question 11

Which of the following is NOT a characteristic of polygenic traits?

Accepted Answer

They are always inherited in a Mendelian 3:1 ratio.

Question 12

A man with normal hearing (dominant) and a woman who is a carrier for tone deafness (recessive) have a child. What is the probability that their child will be tone deaf? Assume the man is homozygous dominant.

Accepted Answer

$$0$$

Question 13

Which of the following is an example of a recessively inherited disorder?

Accepted Answer

Cystic fibrosis

Question 14

If a trait is X-linked recessive, which of the following is most likely to be affected?

Accepted Answer

Males, because they have only one X chromosome

Question 15

Which of the following best describes the effect of penetrance and expressivity on phenotypes?

Accepted Answer

Penetrance determines whether a phenotype is expressed at all, while expressivity determines the degree to which it is expressed.

Question 16

A child is born with phenylketonuria (PKU), a recessive disorder. Both parents are healthy. What are the genotypes of the parents?

Accepted Answer

Both are heterozygous carriers.

Question 17

Which of the following is a correct prediction for the offspring of a dihybrid cross (AaBb x AaBb) assuming independent assortment?

Accepted Answer

$$9:3:3:1$$ phenotypic ratio

Question 18

Which of the following is an example of a dominant trait that cannot be seen (no physical phenotype)?

Accepted Answer

Immunity to poison ivy

Question 19

A woman with type O blood (genotype ii) and a man with type AB blood (genotype IAIB) have children. What are the possible blood types of their children?

Accepted Answer

A and B

Question 20

Which of the following best explains why a person with the genotype Aa for a recessive disorder does not show symptoms of the disorder?

Accepted Answer

The dominant allele produces enough functional protein to mask the effect of the recessive allele.

Mendelian Genetics: Principles, Patterns, and Human Applications (Ch. 14.1–14.4)

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