PCB3063: Chapter 13

silent, missense, nonsense, frameshift

In this figure, the normal DNA coding sequence of a gene is shown on top, along with four different mutations. Match the mutation to its appropriate description.

It replaces the base thymine, and can base pair with guanine rather than adenine.

In which of the following ways does 5-bromouracil cause a mutation?

short wavelength and high energy

Ionizing radiation is characterized by ______.

cytosine

Nitrous acid changes the base adenine to hypoxanthine, which pairs with the base _____. This leads to mutations in the newly-synthesized DNA strand during DNA replication.

deamination

Nitrous acid is a mutagen that acts via the process of ______.

ultraviolet light

Thymine dimers are typically caused by ______.

pyrimidine dimers

Ultraviolet light causes the formation of crosslinked _______in DNA.

A mutation in an embryonic kidney cell A mutation in an adult muscle cell

Which are examples of somatic mutations?

A base deletion, addition

Which changes can cause a frameshift mutation?

X-rays and gamma rays

Which of the following are examples of ionizing radiation?

A to T G to C A to C

Which of the following base changes are transversion mutations?

A to G

Which of the following base changes is a transition mutation?

contains low energy includes ultraviolet light

Which of the following statements about nonionizing radiation are true?

the ames test

Which of these tests is used to evaluate the mutagenicity of an agent?

Mutagens

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

mutant

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

several different

Bacteria possess ______ DNA repair systems.

mutator

Bacterial strains that lack one or more DNA repair systems have a very high mutation rate. These are called _____ strains.

wild-type

In a natural population, a _____-____ genotype is the most common one.

wild-type

In a natural population, a _______-______ genotype is the most common one.

Another negatively-charged amino acid

In a neutral mutation, a negatively-charged amino acid is substituted for ______.

Rat liver extract + Salmonella bacteria that cannot synthesize histidine

In the Ames test for mutagenicity, the control sample contains what?

Cells that produce sperm and eggs

The term germ line is used to describe the

Rat liver contains enzymes that can activate the mutagen.

Why is rat liver extract used in the Ames test for mutagenicity?

The results are less relevant to mammals

You are using the Ames test to assay the mutagenicity of a compound. However, you forgot to add the rat liver extract. What can you say about the results?

Silent

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

Nonsense

A mutation that results in a premature termination of the synthesis of a polypeptide is called a(n) _______mutation.

change to the amino acid sequence of the polypeptide

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

Neutral

A(n) _____ mutation is a missense mutation that has no detectable effect on protein function.

Point

A(n) ______ mutation refers to a mutation in which just one base is changed within the DNA sequence.

Transition

A(n)______ is a type of base substitution that involves a change of a pyrimidine to another pyrimidine, or a purine to another purine.

analog; AT base pair to a GC base pair

5-bromouracil is a base ______ that changes a(n) ______.

missense

A base substitution in DNA that ultimately leads to a change in the encoded amino acid is called a(n) ________mutation.

Transversion

A base substitution in which a purine and a pyrimidine are interchanged is called a(n) ______mutation.

Point

A change in a single base pair in the genetic material is known as a(n) _________mutation.

Substitution

A change of one base for another is described as a base ____________mutation.

mismatch

During DNA replication, a base that does not obey the normal AT/GC base pairing rule is added. This type of mutation is most likely corrected by ____ the repair system.

ionizing

Gamma rays and X-rays are examples of a type of radiation called _____ radiation

ionizing

Gamma rays and X-rays are examples of a type of radiation called __________radiation.

modifying bases and thus altering their normal base-pairing properties

Nitrous acid causes mutations by ______.

frameshift

The addition or deletion of a number of bases that is not a multiple of 3 causes a(n) ______mutation.

Mutation

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

mismatch repair system

If the proofreading ability of a DNA polymerase fails, which of the following DNA repair systems is most likely to detect the resulting mutations and fix them?

somatic

Mutations in body cells that do not go on to form gametes are known as ______ mutations.

The degeneracy of the genetic code

What is responsible for silent mutations?

Nonsense mutations

What type of mutations involve a change from a normal codon to a stop codon?

significantly higher than that of the control plate

A chemical agent is being assayed for mutagenicity using the Ames test. This agent would be judged to be a mutagen if the number of bacterial colonies on the test plate is ______.

agent that causes mutations

A mutagen is a(n) ______.

Has a different DNA sequence from the wild-type

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

Missense

A mutation in a gene that causes an amino acid change in the encoded protein is called a ______ mutation.

germ line

Cells that give rise to the gametes such as eggs and sperm are called _______.

oxidative DNA damage

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

cytosine

Nitrous acid changes the base adenine to hypoxanthine, which pairs with the base ______. This leads to mutations in the newly-synthesized DNA strand during DNA replication.

long wavelength with low energy

Nonionizing radiation is characterized by ______.

bulky, helix distorting lesions

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

Reactive oxygen species

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

reactive oxygen species

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

X-ray and UV lights

Physical mutagens include _____

reactive oxygen

Products of oxygen metabolism, such as hydrogen peroxide, superoxide, and hydroxyl radical, are collectively called __________ species.

products of oxygen metabolism in all aerobic organisms

Reactive oxygen species (ROS) are ______.

Degenerate

Silent mutations are possible because the genetic code is ______.

nucleotide excision repair

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.

gene mutations

The Ames test assays whether an agent causes ______.

histidine

The Ames test uses a strain of the bacterium Salmonella typhimurium that is unable to produce the amino acid ___________.

Uracil, Hypoxanthine

The mutagen nitrous acid changes cytosine to______ and adenine to _______.

Typically

The wild type genotype or phenotype is the one that is ______ found in nature.

Base substitution

This figure best illustrates what type of mutation?

short wavelength gamma rays high energy

Which of the following terms is associated with ionizing energy?

Nitrous acid nitrogen mustard 2- aminopurin 5-bromouracil

Which of these are examples of mutagens?