Genetics Chapter 19: Gene Mutation, DNA Repair and Recombination

Double-strand breaks are typically repaired by which of the following? a. Homologous recombination repair b. Nucleotide excision repair c. Methyl-directed mismatch repair d. Photoreactivation e. Non-homologous end joining

a and e

Nucleotide excision repair (NER) is the main system used in the repair of ______.

bulky, helix distorting lesions

In this figure, two panels are shown. Panel I shows protein A. A first mutation inhibits the function of protein A. In Panel II a second mutation alters protein B to carry out the function of protein A. What is this an example of?

intergenic suppression

The figure shows an example of a(n) ___ ____ mitation

intragenic suppressor

Translesion DNA polymerases are ______ accurate and ______ sensitive to geometric distortions in DNA than replicative DNA polymerases.

less, less

Changes to DNA structure caused by reactive oxygen species (ROS) are termed ____ _____ _____.

oxidative DNA damage

Errors in DNA replication are example of ___ mutations, while mutations caused by ultraviolet light are ____ mutations.

spontaneous, induced

In recombination, what is the process that synthesizes small stretches of DNA to replace those removed by strand degradation?

DNA gap repair synthesis

The first proposal for a set of steps at the molecular level that lead to homologous recombination is called the ____ model.

Holliday

Which model for recombination involves production of single-strand breaks in each of the non-sister chromatids after which the strands invade the opposite helices?

Holliday model

True or False: Most DNA repair systems involve three major steps: detection of the error, removal of the abnormality, and its replacement with normal DNA.

True

Homologous recombination is a process in which

a new combination of DNA sequences is formed through breakage and rejoining of similar or identical DNA segments.

Base excision repair (BER) is the main system used in the repair of ______.

abnormal bases

This figure best illustrates what type of mutation?

base substitution

A silent mutation is a mutation that results in no _____.

change to the amino acid sequence of the polypeptide

The removal of a purine from DNA is called

depurination

Trinucleotide repeat expansions are repeated sequences of three nucleotide bases which ______.

increase generation after generation

Some errors create bulky distortions of the double helix. These errors are removed primarily by a DNA repair system called NER, which stands for ____ _____ repair.

nucleotide excision

The process by which thymine dimers are directly repaired with the help of light is called _____.

photoreactivation

A change of one base for another is describes as a base ____ mutation

point (also substitution)

In addition to the DNA strands of the chromosomes involved in homologous recombination, the multiple steps in the pathway require the action of ____.

protein catalysts

The phenomenon in which a repeated sequence of three nucleotide bases increases in number generation after generation is called ____ _____ ____.

trinucleotide repeat expansion

Translesion DNA polymerases incorporate wrong nucleotides with a frequency of approximately _____, which is ______ than the error rate for replicative DNA polymerases. Multiple choice question.

10^-2, higher

Physical mutagens include ______

both X-rays and UV light

The region where two chromosome pieces break and re-attach to other chromosome pieces is called a chromosomal ______

breakpoint

Which of these tests is used to evaluate the mutagenicity of an agent? a. the Pasteur test b. the Kirby-Bauer test c. The Ames test d. The Phenol coefficient test

c (The Ames test)

The term germ line is used to describe the _____

cells that produce sperm and eggs

A mutant allele is best defined as an allele that ____.

has a different DNA sequence from the wild-type

The process by which chromosomes exchange similar or identical DNA segments during meiosis is called ______.

homologous recombination

An agent that can change DNA structure and cause mutations is known as a(n) ______.

mutagen

An allele that has a DNA sequence different from that of the wild-type is called a(n) ____ allele.

mutant

The multiple steps of homologous recombination, including strand breakage and rejoining, require the action of ______.

protein catalysts

The figure shows a technique known as ____ ____.

replica plating

Mutations can be caused in two ways: (1) ____ mutations are the result of natural biological or chemical processes; and (2) ____ mutations are produced by environmental agents

spontaneous, induced

Mutations that occur in a promoter sequence can be divided into two types: ____ promoter mutations increase the transcription rate, while ___ promoter mutations decrease it.

up, down

Which of the following are examples of base pair mismatches? a. Cytosine on parent strand and Guanine on daughter strand b. Adenine on parent strand and Cytosine on daughter strand c. Cytosine on parent strand and Thymine on daughter strand d. Adenine on parent strand and Thymine on daughter strand e. Cytosine on parent strand and Adenine on daughter strand

b, c and e

Some errors affect individual nucleotides and do not distort the DNA double helix. These errors are removed primarily by a DNA repair system called BER, which stands for _____ _____ repair.

base excision

During the normal course of DNA replication, the addition of a nucleotide that does not obey the AT/GC rule of base pairing creates a ______.

base pair mismatch

Photoreactivation is a repair mechanism that can ______ a thymine dimer in the ______ of light.

directly split, presence

The mutation rate is commonly expressed at the number of new mutations in a given ______

gene per cell generation

The two main mechanisms used to repair DNA double-strand breaks are ____ recombination repair and _____ end jointing.

homologous, non-homologous

A heritable change in the genetic material is called an _____

mutation

The term ____ refers to an inherited change in the sequence of the genetic material

mutation

The probability that a gene will be altered by a new mutation is referred to as the ____.

mutation rate

Which of these are examples of mutagens? nitrogen mustard, 5-Bromouracil, cytosine, nitrous acid, 2-Aminopurine, Guanine, Adenosine triphosphate

nitrogen mustard, 5-Bromouracil, nitrous acid, 2-aminopurine

Oxidative DNA damage refers to changes in DNA structure that are caused by ______.

reactive oxygen species (ROS)

If a heteroduplex includes a region with an allelic difference, the cell will ______.

repair the mismatch to either the dominant or recessive allele

DNA gap repair synthesis

restores the stretches of DNA removed by strand degradation at the initiation of recombination.

A mutation that does not change the amino acid sequence of a polypeptide is known as a(n) ____ mutation.

silent

Mutations that remove an adenine or guanine from the DNA are known as ______.

depurinations (A and G are purines)

The Ames test assays whether an agent causes ___ ___.

gene mutations

Which of the following statements about promoter mutations is true? a. Up promoter mutations occur in the coding sequence of the gene b. Up promoter mutations cause the promoter sequence to be more like the consensus sequence c. Down promoter mutations occur in the 3'-UTR of the gene d. down promoter mutations decrease the affinity of transcription factors to the promoter

b and d (up causes them to be more like the consensus sequence and down causes them to be less like the consensus sequence)

Which of these represents the correct order of steps during a typical DNA repair system? a. detection, replication, removal b. detection, removal, replication c. replication, detection, removal d. replication, removal, detection

b (detection, removal, replication)

A breakpoint refers to the region _____.

where two chromosome pieces break and rejoin with other chromosome pieces

Gene conversion occurs by the action of ______ a. Spoll double strand breaks b. DNA gap repair synthesis c. mismatch repair d. base excision repair

b and c (mismatch repair and DNA gap repair synthesis)

Replica plating is a technique in which _____.

bacterial colonies are transferred from one plate to another with a sterile piece of velvet cloth