Question 1

Which of the following best describes the concept of 'haplosufficiency' in gene function?

Accepted Answer

A single copy of a wild-type allele is sufficient to produce a normal phenotype.

Question 2

A cross between two heterozygous yellow mice (A^Y A) results in a 2:1 ratio of yellow to agouti offspring. What is the most likely explanation for the missing genotype?

Accepted Answer

The A^Y A^Y genotype is embryonic lethal.

Question 3

Which of the following is an example of a dominant negative mutation?

Accepted Answer

A mutation in one subunit of a multimeric protein that disrupts the function of the entire complex.

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 plant with genotype $$T_1$$ $$T_2$$ for a gene showing incomplete dominance flowers later than $$T_1$$ $$T_1$$ but earlier than $$T_2$$ $$T_2. $$What is the phenotype of $$T_1$$ $$T_2$$ plants?

Accepted Answer

Intermediate flowering time between $$T_1$$ $$T_1$$ and $$T_2$$ $$T_2$$

Question 6

Which of the following best describes pleiotropy?

Accepted Answer

A single gene mutation affects multiple distinct traits.

Question 7

A cross between two white-flowered sweet peas (from different pure-breeding lines) produces all purple F1 offspring. When F1 plants are selfed, the F2 generation shows a 9:7 ratio of purple to white flowers. What genetic interaction is most likely responsible?

Accepted Answer

Complementary gene interaction

Question 8

In Labrador retrievers, coat color is determined by two genes: one for pigment production (B, b) and one for pigment deposition (E, e). If a dog has genotype $$B_Ee$$, what is the expected coat color?

Accepted Answer

Black

Question 9

Which of the following phenotypic ratios is expected from a dihybrid cross showing duplicate gene action?

Accepted Answer

$$15:1$$

Question 10

A patient with phenylketonuria (PKU) can avoid symptoms by following a strict diet low in phenylalanine. This is an example of:

Accepted Answer

Gene–environment interaction

Question 11

Which of the following best explains incomplete penetrance?

Accepted Answer

Not all individuals with a genotype express the expected phenotype.

Question 12

A mutation that results in a gene product with increased activity compared to the wild type is called:

Accepted Answer

Hypermorphic mutation

Question 13

Which of the following is true about codominance?

Accepted Answer

Both alleles are fully expressed in the heterozygote.

Question 14

In a dihybrid cross, which gene interaction produces a $$12:3:1$$ phenotypic ratio?

Accepted Answer

Dominant epistasis

Question 15

A goat breed shows beards only in males with genotype $$B_1B_2$$, but not in females with the same genotype. This is an example of:

Accepted Answer

Sex-influenced trait

Question 16

Which of the following is a characteristic of a neomorphic mutation?

Accepted Answer

It produces a novel function not found in the wild type.

Question 17

A cross between two disk-shaped summer squash plants (A_B_) produces offspring in a 9:6:1 ratio of disk:round:long fruit. What type of gene interaction is this?

Accepted Answer

Dominant gene interaction

Question 18

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

Accepted Answer

It produces a reduced amount of functional gene product.

Question 19

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

Accepted Answer

Milk production in mammals

Question 20

A dihybrid cross produces a 13:3 phenotypic ratio in the F2 generation. Which gene interaction is most likely responsible?

Accepted Answer

Dominant suppression

Gene Interactions: Mechanisms, Phenotypes, and Modified Mendelian Ratios

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