Chapter 15 practice questions

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?

1. a base substitution at the beginning of the gene
2. a base substitution at the end of the gene
3. a frameshift deletion at the beginning of the gene
4. a frameshift deletion at the end of the gene

3. a frameshift deletion at the beginning of the gene

Tautomers of nucleotide bases are isomers that differ from each other in the location of one hydrogen atom in the molecule.

1. True
2. False

1. True

Which nucleotide will base‑pair with the enol form of 5‑bromouracil?

1. Guanine
2. Adenine
3.Cytosine
4. Thymine

1. Guanine

Which of the following events could result in a frameshift mutation?

1. Base deletion
2.Incorporation of base analogs
3.Tautomeric shift
4.Point mutation

1. Base deletion

In terms of its involvement in mutagenesis, 5BU is best described as _______.

1. a chemical that alters the structure of nitrogenous bases
2. a base analog that can cause either A-T > G-C or G-C > A-T transitions
3. a base analog that, if incorporated into a DNA molecule during replication, remains permanently in its rare form
4. a rare form of adenine that can base pair with cytosine

2. a base analog that can cause either A-T > G-C or G-C > A-T transitions

For 5BU to cause a transition mutation, which of the following must occur?

1. It must be incorporated into DNA in its rare form.
2.DNA with incorporated 5BU must not replicate.
3. It must undergo at least two form changes.
4. DNA with incorporated 5BU must replicate.

4. DNA with incorporated 5BU must replicate.

In its rare form, 5BU pairs with guanine.

1. True
2.False

1. True

Which enzyme is responsible for proofreading during replication?

1.DNA polymerase
2. DNA ligase
3.DNA glycosylase
4.RNA polymerase

1.DNA polymerase

Bacteria can distinguish between a newly replicated DNA strand and the original template strand because the newly replicated strand is methylated, whereas the original template strand is not.

1. True
2. False

2. False

Which repair system uses the RecA and LexA proteins?

1.Photoreactivation repair
2.Mismatch repair
3.Proofreading repair
4. SOS repair

4. SOS repair

The purpose of the Ames Test is to _______.

1. determine whether histidine has mutagenic effects in S. typhimurium
2.study how the liver affects potential mutagens
3. determine whether Salmonella typhimurium his- mutants can revert to his+
4. test the mutagenic effects of chemicals

4. test the mutagenic effects of chemicals

In the Ames Test, the appearance of his+ revertants in the presence of a non-mutagenic control compound indicates that _______.

1.some of the reversion mutations are not caused by the mutagen being tested
2.liver extract increases the potency of some mutagens
3. the growth medium contains factors that are mildly mutagenic
4.there is some low-level contamination in most experiments

1.some of the reversion mutations are not caused by the mutagen being tested

Many chemicals are more mutagenic after being processed in the liver.

1. True
2. False

1. True

A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?

1. transition
2. frameshift
3. recombinant
4. transversion
5.base analog

2. frameshift

Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.

1. sense and antisense
2.euchromatic and heterochromatic
3.error prone and spontaneous
4.base analogs and frameshift
5. transversions and transitions

5. transversions and transitions

Loss-of-function mutations eliminate the function of a gene product and may be dominant or recessive.

True
False

True

Of the two cell lines that can contain a mutation in an organism, somatic and germ line, the latter is more consequential to subsequent generations.

True
False

True

A point mutation occurs such that a codon is changed from AGA to AGC. Which term describes this mutation?

Frameshift mutation
Transversion mutation
Transition mutation
Insertion mutation

Transversion mutation

Mutations that arise in nature, from no particular artificial agent, are called ________.

chromosomal aberrations
oblique mutations
cosmic mutations
spontaneous mutations
induced mutations

spontaneous mutations

Which of the following are two mutagens that would be classified as base analogs?

acridine orange and proflavin
ethylmethane sulfonate and ethylmethylketone peroxide
hydroxyurea and peroxidase
ultraviolet light and cosmic radiation
5-bromouracil and 2-aminopurine

5-bromouracil and 2-aminopurine

Apurinic sites (AP sites) involve a spontaneous loss of a(n)________ in an intact double-helix DNA molecule.

purine

When treating an organism with a mutagen, although it is possible that homozygous mutations will occur, it is more likely that most new mutations will be heterozygous or hemizygous.

True
False

True

Considering the electromagnetic spectrum, identify likely mutagens from the following list: radio waves, microwaves, infrared, ultraviolet, X-rays, gamma rays, cosmic rays.

cosmic rays
microwaves
radio waves
ultraviolet
X-rays
infrared
gamma rays

cosmic rays ultraviolet X-rays gamma rays

The shorter the wavelength of a radiation source, the greater its likelihood of causing damage.

True
False

True

Certain base analogs such as 5-bromouracil cause mutations by chemically altering nitrogenous bases in nonreplicating DNA.

True
False

False

What are the consequences of having pyrimidine dimers in DNA?

These dimers distort the DNA structure and result in errors during DNA replication.
They form an extra phosphodiester bond between them.
They prevent the transcription of the DNA into RNA.
They create an apyrimidinic site

These dimers distort the DNA structure and result in errors during DNA replication.

Thymine dimers can be repaired by Photoreactivation Repair or Nucleotide Excision Repair.

True
False

True

Which of the following statements regarding Nucleotide Excision Repair (NER) and Base Excision Repair (BER) is true?

Both NER and BER involve the creation of an apyrimidinic (AP) site.
Both NER and BER can be activated by exposure to visible light.
Only NER involves the action of DNA ligase to seal nicks in the DNA backbone.
Both NER and BER involve the removal of one or more damaged bases by a nuclease.

Both NER and BER involve the removal of one or more damaged bases by a nuclease.

Strand discrimination during the process of DNA repair is based on DNA methylation in E. coli.

True
False

True

Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates. Such individuals are likely to suffer from ________.

phenylketonuria
muscular dystrophy
xeroderma pigmentosum
SCID
Huntington disease

xeroderma pigmentosum

The process of error correction of mismatched bases carried out by DNA polymerases is called ________.

proofreading

Which enzyme is responsible for proofreading during replication?

RNA polymerase
DNA polymerase
DNA glycosylase
DNA ligase

DNA polymerase

Transposons, or jumping genes, are DNA elements that move within the genome. In which organismic groups are transposons found?

ancient bacteria
eukaryotes
mammals
bacteria
all organismic groups

all organismic groups

All insertion sequences (IS elements) contain two features that are essential for their movement. What are these two elements?

proto-oncogenes and oncogenes
transposase and oncogenes
transposase and inverted terminal repeats
integrase and pseudogenes
integrase and oncogenes

transposase and inverted terminal repeats

Bacterial transposons contain more genes than insertion sequences.

True
False

True

What is the common influence of ultraviolet light on DNA?

generation of pyrimidine dimers

A missense mutation causes premature chain termination

True
False

False

In the first step of base excision repair

1. a phosphodiester bond is broken
2. two nicks are made surrounding the DNA damage
3. a break in DNA is sealed by DNA ligase
4. a base is removed by the action of a DNA glycosylase

4. a base is removed by the action of a DNA glycosylase