Question 1

Which of the following best describes a transposon?

Accepted Answer

A DNA sequence that can move from one genomic location to another via a cut-and-paste or copy-and-paste mechanism.

Question 2

Which enzyme is required for the mobilization of retrotransposons?

Accepted Answer

Reverse transcriptase

Question 3

A mutation in the lacI gene that results in a nonfunctional repressor protein will have what effect on the lac operon?

Accepted Answer

The lac operon will be constitutively expressed, regardless of lactose presence.

Question 4

Which of the following mutations can result in constitutive expression of the lac operon?

Accepted Answer

Mutations in either lacI or lacO

Question 5

You perform a test cross of an RrBb plant (where R and B are unlinked genes) and obtain 16 progeny. If the presence of gene product B is required for pigment, and gene product R is required for red pigment, how many progeny do you expect to have white berries?

Accepted Answer

$4$

Question 6

In a dihybrid cross involving two linked genes, the parental types are observed at a much higher frequency than the recombinant types. What does this indicate about the genes?

Accepted Answer

The genes are close together on the same chromosome.

Question 7

A complementation test is performed between two mutant strains, and the resulting progeny display the wild-type phenotype. What does this indicate?

Accepted Answer

The mutations are in different genes.

Question 8

Which of the following best describes a dominant negative mutation?

Accepted Answer

A mutant allele whose gene product interferes with the function of the wild-type protein.

Question 9

If two genes are 10 map units apart, what is the expected recombination frequency between them?

Accepted Answer

$10\%$

Question 10

Which of the following is a key difference between a genetic map and a physical map?

Accepted Answer

A genetic map is based on recombination frequencies, while a physical map is based on actual DNA sequence distances.

Question 11

Which of the following statements about CRISPR-Cas9 is correct?

Accepted Answer

The guide RNA directs Cas9 to a specific DNA sequence, which is then cut by Cas9.

Question 12

A bacterial strain that can grow on minimal medium without supplementation is called:

Accepted Answer

A prototroph

Question 13

Which of the following is NOT a possible outcome of homologous recombination?

Accepted Answer

Constitutive expression of an operon

Question 14

In a three-point test cross, the gene order is determined by:

Accepted Answer

Identifying the double crossover progeny and comparing them to the parental types.

Question 15

Which of the following best describes a neomorphic mutation?

Accepted Answer

A mutation that results in a protein with a novel function not found in the wild-type.

Question 16

A fly is heterozygous for two linked genes, pr and vg. If the pr and vg alleles are in cis configuration, which of the following represents the arrangement of alleles on the homologous chromosomes?

Accepted Answer

$pr^+\ vg^+\ /\/\ pr\ vg$

Question 17

Which of the following is a consequence of transposition in the genome?

Accepted Answer

Insertional mutagenesis leading to gene disruption

Question 18

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

Accepted Answer

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

Question 19

Which of the following is required for a CRISPR-Cas9 reaction to successfully cut a target DNA?

Accepted Answer

A guide RNA complementary to the target and a PAM sequence adjacent to the target site.

Question 20

A gain-of-function (GOF) mutation is usually:

Accepted Answer

Dominant

Genetics Exam 3 Review: Key Concepts and Applications

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