Question 1

A woman with blood type AB and a man with blood type O have a child. Which of the following blood types is possible for their child?

Accepted Answer

Type B

Question 2

In Mendel's experiments, the law of segregation states that:

Accepted Answer

Each allele for a trait separates into different gametes during meiosis.

Question 3

A man with normal color vision (not a carrier) and a woman who is a carrier for red-green color blindness (an X-linked recessive trait) have a son. What is the probability that their son will be color blind?

Accepted Answer

$$P = 0.5$$

Question 4

Which of the following best describes codominance?

Accepted Answer

Both alleles are fully expressed in the phenotype of a heterozygote.

Question 5

A dihybrid cross between two heterozygous pea plants ($$RrYy 	imes RrYy) $$produces what phenotypic ratio in the F2 generation, assuming independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 6

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 7

Which of the following scenarios is an example of epistasis?

Accepted Answer

A gene at one locus masks the expression of a gene at a different locus.

Question 8

If a woman who is heterozygous for the sickle cell allele ($$Hb^A Hb^S) $$marries a man who is also heterozygous, what is the probability that their child will have sickle cell disease?

Accepted Answer

$$P = 0.25$$

Question 9

Which of the following best explains why X-linked recessive disorders are more common in males than females?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will cause the disorder.

Question 10

A geneticist is studying two genes on the same chromosome and finds that the observed frequency of recombinant offspring is much lower than 50%. What does this suggest about the genes?

Accepted Answer

The genes are linked and located close together on the chromosome.

Question 11

Which of the following is a consequence of nondisjunction during meiosis?

Accepted Answer

A gamete with an abnormal number of chromosomes, leading to aneuploidy.

Question 12

A woman is a carrier for hemophilia (an X-linked recessive disorder) and her partner is unaffected. What is the probability that their daughter will have hemophilia?

Accepted Answer

$$P = 0.25$$

Question 13

Which of the following best describes polygenic inheritance?

Accepted Answer

A trait is controlled by two or more genes, each with a small additive effect.

Question 14

In a testcross, an individual with an unknown genotype 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 15

A woman with genotype $$X^B X^b ($$where $$B is $$normal vision and $$b is $$color blindness) and a man with genotype $$X^b Y$$ have a child. What is the probability that their daughter will be color blind?

Accepted Answer

$$P = 0.25$$

Question 16

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene causes multiple, seemingly unrelated phenotypic effects.

Question 17

A couple has a child with Down syndrome (trisomy 21). Which of the following most likely occurred during gamete formation?

Accepted Answer

Nondisjunction during meiosis

Question 18

In a cross between two true-breeding pea plants, one with purple flowers (PP) and one with white flowers (pp), all F1 offspring have purple flowers. What is the genotype and phenotype ratio in the F2 generation after self-fertilization of the F1 plants?

Accepted Answer

Genotype $$1:2:1 (PP$$:Pp:pp), Phenotype $$3:1 ($$purple:white)

Question 19

Which of the following best describes the wild type in genetic experiments?

Accepted Answer

The phenotype most commonly observed in natural populations

Question 20

A researcher uses the chi-squared test to analyze the offspring of a dihybrid cross and finds a significant deviation from the expected $$9:3:3:1$$ ratio. What is the most likely explanation?

Accepted Answer

The genes are linked and do not assort independently.

Genetics: Mendelian and Chromosomal Basis of Inheritance

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