Question 1

Marfan syndrome is caused by a mutation in a single gene, FBN1, but results in multiple seemingly unrelated symptoms (skeletal, cardiovascular, and eye). What genetic concept does this illustrate?

Accepted Answer

Pleiotropy

Question 2

A dihybrid cross between two genes with no interaction produces a phenotypic ratio of $$9:3:3:1. $$What does this ratio indicate about the relationship between the two genes?

Accepted Answer

The genes assort independently and do not interact

Question 3

In a dihybrid cross of Ww and Cc cats, both genes are required for pigment production. If a cat is cc, what is the expected phenotype?

Accepted Answer

White

Question 4

Which type of gene interaction results in a $$13:3$$ phenotypic ratio in a dihybrid cross?

Accepted Answer

Dominant suppression epistasis

Question 5

A biosynthetic pathway for methionine involves several enzymes, each encoded by a different gene. Which hypothesis does this support?

Accepted Answer

One gene-one enzyme hypothesis

Question 6

A complementation test is performed by crossing two true-breeding mutants with the same phenotype. If the F1 offspring are wild-type, what does this indicate?

Accepted Answer

The mutations are in different genes

Question 7

In the case of Mexican cavefish, blindness is recessive and controlled by multiple genes. If two blind fish from different caves are crossed and their offspring can see, what does this suggest?

Accepted Answer

The mutations are in different genes

Question 8

Which of the following is an example of complementary gene interaction?

Accepted Answer

Both genes must have at least one dominant allele for the phenotype to be expressed

Question 9

A plant with genotype $$ccPP is $$crossed with a plant with genotype $$CCpp. $$All F1 offspring are $$CcPp$$ and have purple flowers. What does this result demonstrate?

Accepted Answer

Complementation

Question 10

Which of the following best describes epistasis?

Accepted Answer

An allele of one gene modifies or prevents the expression of alleles of another gene

Question 11

In a dihybrid cross involving duplicate gene interaction, what is the expected phenotypic ratio?

Accepted Answer

$$15:1$$

Question 12

A child is born to two parents, each from a family with recessive hereditary deafness, but the deafness is caused by mutations in different genes in each family. What is the expected hearing status of the child?

Accepted Answer

The child will have normal hearing

Question 13

Which of the following is NOT a type of loss of function (LOF) mutation?

Accepted Answer

Hypermorphic

Question 14

In a metabolic pathway, a mutation in the gene encoding the first enzyme blocks the entire pathway. What is the effect on the phenotype?

Accepted Answer

The end product is not produced

Question 15

Which equation represents the expected phenotypic ratio for a dihybrid cross with complementary gene interaction?

Accepted Answer

$$9:7$$

Question 16

If a mutation in gene A prevents the conversion of precursor 1 to precursor 2, and a mutation in gene B prevents the conversion of precursor 2 to pigment, what is the result of crossing two mutants (one for each gene)?

Accepted Answer

All offspring will be wild-type

Question 17

Which of the following statements about complementation analysis is TRUE?

Accepted Answer

It only works for recessive alleles

Question 18

A mutation that increases the activity of a gene product beyond normal levels is called:

Accepted Answer

Hypermorphic

Question 19

Which pathway type is involved when information from outside the cell is converted into a response inside the cell?

Accepted Answer

Signal transduction pathway

Question 20

In a dihybrid cross of WwCc cats, how many out of 16 offspring are expected to be white if both genes are required for pigment production?

Accepted Answer

$$13$$

Epistasis and Complementation: Gene Interactions in Genetics

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