Question 1

A wild-type allele (R+) produces 50 units of enzyme activity, while a mutant allele (r) produces 0 units. If 40 or more units are required for a wild-type phenotype, which genotype(s) will display the mutant phenotype?

Accepted Answer

$$rr$$ only$

Question 2

Which of the following best describes a dominant negative mutation?

Accepted Answer

A mutation that produces a nonfunctional protein that interferes with the function of the normal protein in multimeric complexes

Question 3

A patient with phenylketonuria (PKU) is able to live a normal life if they follow a strict diet low in phenylalanine. This is an example of:

Accepted Answer

Gene–environment interaction

Question 4

In the ABO blood group system, which genotype(s) will result in blood type AB?

Accepted Answer

$$I^A I^B$$

Question 5

A gene has four alleles: $$C$$, $$c^{ch}$$, $$c^h$$, and $$c. $$The dominance hierarchy is $$C \u003e c$$^{ch}$$ \u003e c^h \u003e c. $$Which genotype would result in a Himalayan phenotype in rabbits?

Accepted Answer

$$c^h c^h$$

Question 6

Which of the following is an example of incomplete dominance?

Accepted Answer

A heterozygote displays a phenotype intermediate between the two homozygotes

Question 7

A woman with polydactyly (an autosomal dominant trait) has five fingers on each hand. Her son, who inherited the same allele, has six fingers on one hand and seven on the other. This is an example of:

Accepted Answer

Variable expressivity

Question 8

Which of the following best describes a leaky (hypomorphic) mutation?

Accepted Answer

A mutation that produces a small amount of functional gene product

Question 9

A man with genotype $$B_1B_2$$ for a sex-influenced trait is bearded, while a woman with the same genotype is beardless. What does this illustrate?

Accepted Answer

Sex-influenced inheritance

Question 10

Which of the following is a real-world example of pleiotropy?

Accepted Answer

Sickle cell disease affecting multiple organ systems

Question 11

A gene product is only functional at low temperatures, resulting in pigment only on the extremities of an animal. This is an example of:

Accepted Answer

A temperature-sensitive hypomorphic mutation

Question 12

Which of the following best describes codominance?

Accepted Answer

Both alleles are fully expressed in the heterozygote

Question 13

In a population, a gene has multiple alleles with a clear order of dominance. This is referred to as:

Accepted Answer

An allelic series

Question 14

A mutation in a gene results in a protein with a new function not found in the wild type. This is best described as:

Accepted Answer

A neomorphic mutation

Question 15

Which of the following scenarios best illustrates incomplete penetrance?

Accepted Answer

Some individuals with the genotype do not show the phenotype at all

Question 16

A wild-type allele is described as haplosufficient. What does this mean?

Accepted Answer

One copy is sufficient for normal function

Question 17

Which of the following best describes the molecular basis of the O blood type in the ABO system?

Accepted Answer

The O allele encodes a nonfunctional enzyme, leaving the H antigen unmodified

Question 18

Which of the following is a real-world example of gene–environment interaction?

Accepted Answer

Seasonal changes in coat color in arctic animals

Question 19

A pathway for pigment production in a plant requires the action of two enzymes, each encoded by a different gene. A mutation in either gene results in a white flower. This is an example of:

Accepted Answer

Epistasis

Question 20

Which of the following best describes a gain-of-function hypermorphic mutation?

Accepted Answer

A mutation that produces more gene activity than normal

Gene Interaction and Extensions to Mendelian Inheritance

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