Question 1

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes contribute additively to a continuous trait.

Question 2

A geneticist performs a complementation analysis by crossing two mutants with the same phenotype. The F1 offspring also display the mutant phenotype. What can be concluded?

Accepted Answer

The mutations are in the same gene.

Question 3

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

Accepted Answer

$$9:3:4$$

Question 4

A researcher finds 10 different mutants, all with the same phenotype. A complementation matrix shows 4 complementation groups. How many genes are responsible for the phenotype?

Accepted Answer

4

Question 5

Which of the following statements about epistasis is FALSE?

Accepted Answer

Epistasis can occur when only a single gene controls a phenotype.

Question 6

In dominant epistasis, what is the expected phenotypic ratio in the F2 generation of a dihybrid cross?

Accepted Answer

$$12:3:1$$

Question 7

Morning glories can be blue, purple, or red depending on alleles at two loci (A and B): $$A	extunderscore B	extunderscore = $$blue, $$A	extunderscore bb or$$ $$aa B	extunderscore = $$purple, $$aa bb = $$red. If two $$AaBb$$ plants are crossed, what is the phenotypic ratio?

Accepted Answer

$$9:6:1$$

Question 8

A human disease is found to be caused by mutations in any one of several genes. Patients with mutations in different genes can have the same symptoms. Which genetic principle does this illustrate?

Accepted Answer

Complementation

Question 9

In a dihybrid cross, the F2 generation shows a $$9:7$$ phenotypic ratio. Which type of gene interaction is most likely responsible?

Accepted Answer

Complementary epistasis

Question 10

Which of the following best explains why polygenic traits, such as human height, show continuous variation?

Accepted Answer

Multiple genes contribute additively to the phenotype.

Question 11

A dihybrid cross produces a $$15:1$$ phenotypic ratio in the F2 generation. Which type of epistasis does this indicate?

Accepted Answer

Duplicate epistasis

Question 12

In a complementation test, two white-flowered petunia mutants are crossed and the F1 offspring are all purple. What does this indicate?

Accepted Answer

The mutations are in different genes.

Question 13

Which of the following is a real-world example of recessive epistasis?

Accepted Answer

Labrador retriever coat color

Question 14

A dihybrid cross between $$AaBb$$ individuals results in the following F2 phenotypic ratio: $$13:3. $$Which type of gene interaction is this?

Accepted Answer

Dominant suppression

Question 15

If a trait is controlled by two genes and the presence of at least one dominant allele at either locus produces the same phenotype, what is the expected F2 phenotypic ratio?

Accepted Answer

$$15:1$$

Question 16

Which of the following statements about complementation analysis is correct?

Accepted Answer

It helps determine if mutations are in the same or different genes.

Question 17

A dihybrid cross in squash produces disk, sphere, and long fruit shapes in a $$9:6:1$$ ratio. What type of gene interaction is this?

Accepted Answer

Dominant interaction

Question 18

In a complementation matrix, a '-' symbol between two mutants means:

Accepted Answer

The mutants fail to complement and are in the same gene.

Question 19

Which of the following is a key feature of epistasis?

Accepted Answer

It changes the phenotypic ratio but not the genotypic ratio.

Question 20

A geneticist is studying a disease that can be caused by mutations in any of seven different genes. If she finds 21 different mutant lines, what is the minimum number of complementation groups she should expect?

Accepted Answer

7

Polygenic Inheritance, Complementation, and Epistasis: Advanced Genetics Study Notes

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