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

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

Which nucleotide will base‑pair with the enol form of 5‑bromouracil? 1. Guanine 2. Adenine 3.Cytosine 4. Thymine

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

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

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.

In its rare form, 5BU pairs with guanine. 1. True 2.False

Which enzyme is responsible for proofreading during replication? 1.DNA polymerase 2. DNA ligase 3.DNA glycosylase 4.RNA 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

Which repair system uses the RecA and LexA proteins? 1.Photoreactivation repair 2.Mismatch repair 3.Proofreading 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

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

Many chemicals are more mutagenic after being processed in the liver. 1. True 2. False

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

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

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

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

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

Mutations that arise in nature, from no particular artificial agent, are called ________. chromosomal aberrations oblique mutations cosmic mutations spontaneous mutations induced 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

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

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

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

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

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

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

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.

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

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

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

Which enzyme is responsible for proofreading during replication? RNA polymerase DNA polymerase DNA glycosylase DNA ligase

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 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

Bacterial transposons contain more genes than insertion sequences. True False

What is the common influence of ultraviolet light on DNA?

A missense mutation causes premature chain termination True 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