Question 1

Which of the following statements best describes dosage compensation in mammals?

Accepted Answer

Dosage compensation ensures that both males and females express the same amount of X-linked gene products by randomly inactivating one X chromosome in each female cell.

Question 2

A woman with normal vision has a mother who is color blind (an X-linked recessive trait). She marries a color-blind man. What is the probability that their first child will be color blind?

Accepted Answer

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

Question 3

Which of the following is an example of a sex-influenced trait?

Accepted Answer

Pattern baldness in humans, where the phenotype is influenced by the individual's sex hormones.

Question 4

In Labrador retrievers, coat color is determined by two genes: B (black) is dominant to b (brown), and E (pigment deposition) is dominant to e (no pigment, resulting in yellow). What is the expected phenotypic ratio in the offspring of two dogs with genotype BbEe?

Accepted Answer

$$9$$ black : $$3$$ brown : $$4$$ yellow

Question 5

A gene exhibits 30% penetrance. If 100 individuals have the genotype for a dominant trait, how many are expected to express the phenotype?

Accepted Answer

$$30$$

Question 6

Which of the following best explains the phenomenon of pleiotropy?

Accepted Answer

A single gene affects multiple, seemingly unrelated phenotypic traits.

Question 7

A man with blood type O and a woman with blood type AB have a child. Which blood types are possible for their child?

Accepted Answer

A or B

Question 8

Which of the following is true regarding X-linked recessive inheritance?

Accepted Answer

Affected fathers do not pass the trait to their sons.

Question 9

In a complementation test, two mutant strains are crossed and the offspring display the wild-type phenotype. What does this indicate?

Accepted Answer

The mutations are in different genes.

Question 10

Which of the following is an example of cytoplasmic inheritance?

Accepted Answer

Mitochondrial DNA mutations passed from mother to all offspring.

Question 11

A Siamese cat has darker fur on its extremities due to a temperature-sensitive allele. What is this an example of?

Accepted Answer

Conditional allele

Question 12

Which of the following best describes epistasis?

Accepted Answer

One gene masks the effect of another gene at a different locus.

Question 13

In a dihybrid cross involving two genes with dominant epistasis, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$12:3:1$$

Question 14

Which of the following is a characteristic of sex-limited traits?

Accepted Answer

They are generally autosomal but expressed in only one sex.

Question 15

A trait is controlled by two genes, each with two alleles. If both genes must have at least one dominant allele to express the phenotype, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$9:7$$

Question 16

Which of the following best describes genomic imprinting?

Accepted Answer

The expression of a gene depends on whether it is inherited from the mother or the father.

Question 17

Which of the following is an example of a multifactorial trait?

Accepted Answer

Human skin color, which is influenced by multiple genes and environmental factors.

Question 18

A pedigree shows a trait that is rare, skips generations, and affected fathers do not pass the trait to their sons. Which inheritance pattern is most likely?

Accepted Answer

X-linked recessive

Question 19

Which of the following best describes incomplete dominance?

Accepted Answer

The heterozygote has a phenotype intermediate between the two homozygotes.

Question 20

A woman with genotype $$I^A I^B (AB $$blood type) and a man with genotype $$I^O I^O (O $$blood type) have a child. What is the probability that the child will have blood type A?

Accepted Answer

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

Extensions and Modifications to Inheritance: Genetics Study Notes

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