Deck 16: Mechanisms of Genetic Variation

Question 1

__________ are physical or chemical agents that cause mutation.

Answer 1

Mutagens

Question 2

A mutation that changes the amino acid sequence of the resulting protein by substitution is called a __________ mutation.

A)missense
B)nonsense
C)silent
D)none of the choices

Answer 2

A

Question 3

_______ are strains that are unable to grow on a minimal medium that supports growth of the wild type strain but are able to grow on the minimal medium if one or more nutritional supplements are added.

A)Autotrophs
B)Auxotrophs
C)Prototrophs
D)Minitrophs

Answer 3

B

Question 4

A mutagen that inserts between the stacked bases of a DNA double helix,distorting the DNA to induce single-pair insertions or deletions is called a(n)__________ agent.

A)insertional
B)interspersing
C)intercalating
D)distortional

Question 5

Lethal mutations can be maintained in diploid organisms if they are

A)dominant.
B)recessive.
C)deletions.
D)none of the choices

Question 6

Microbial strains that can grow on minimal medium are called __________.

A)autotrophs
B)auxotrophs
C)prototrophs
D)minitrophs

Question 7

Mutations that result in the death of an organism when expressed are called __________ mutations.

A)dominant
B)recessive
C)lethal
D)conditional

Question 8

Which of the following is considered a reverse mutation that will restore the wild type phenotype?

A)True reversion back to the wild type base sequence.
B)Mutation to a different base sequence,but one that restores the amino acid sequence in the protein to the wild type sequence.
C)A mutation that restores the function of a protein even though it does not restore the base sequence or the amino acid sequence to the wild type.
D)All of the choices.

Question 9

Lethal mutations can be recovered in haploid organisms if they are

A)dominant.
B)active.
C)conditional.
D)none of the choices

Question 10

Which of the following can lead to transition mutations?

A)Incorporation of a base analog that exhibits different base-pairing properties from the base it replaces.
B)Chemical modification of an existing base in the DNA so that in the next round of replication it will pair differently from the unmodified base.
C)Incorporation of a base analog that exhibits different base-pairing properties from the base it replaces and chemical modification of an existing base in the DNA so that in the next round of replication it will pair differently from the unmodified base.
D)A small insertion or deletion.

Question 11

A __________ mutation does not alter the amino acid sequence of the resulting protein.

A)missense
B)nonsense
C)silent
D)none of the choices

Question 12

As the result of exposure to a mutagen,cytosine is substituted for thymine in one strand of DNA.Upon subsequent DNA replication,one of the daughter cells will have a GC pair in this position instead of an AT pair.This is called a(n)__________ mutation.

A)transversion
B)transition
C)frameshift
D)insertion

Question 13

__________ mutations occur in the promoter or operator region of a gene or set of genes and affects the expression of the downstream genes without affecting the amino acid sequences of the gene products.

Question 14

__________ mutations affect only a single base pair in a gene.

Question 15

The __________ __________ is the most prevalent form of a gene in a population.

Question 16

A mutation from the most prevalent form of a gene to a mutant form is called a __________ mutation.

A)forward
B)reverse
C)wild card
D)escalating

Question 17

A __________ mutation is one that causes premature termination of the synthesis of the protein product.

A)missense
B)nonsense
C)silent
D)none of the choices

Question 18

Spontaneous mutations are caused by

A)errors in DNA replication.
B)insertion of transposons.
C)radiation.
D)errors in DNA replication and insertion of transposons
E)all of the choices

Question 19

Which of the following types of mutation may play an important role in driving evolution because they are often nonlethal and,therefore,remain in the gene pool?

A)nonsense
B)missense
C)frameshift
D)deletion

Question 20

Mutations resulting from exposure to physical or chemical agents are called __________ mutations.

Question 21

Repair of an apurinic or apyrimidinic site in DNA by AP endonuclease must be completed by the action of

A)UvrABC endonuclease.
B)RecA protein.
C)DNA polymerase I.
D)none of the choices.

Question 22

When bacterial genes are transferred to another bacterium by a virus,it is called

A)conjugation.
B)transformation.
C)transduction.
D)transfection.

Question 23

SOS repair

A)requires RecA protein.
B)is inducible by DNA damage.
C)is error prone,i.e.,produces mutations.
D)all of the choices

Question 24

Which one of the following contributes to the utility of the strains of Salmonella typhimurium used in the Ames reversion assay?

A)They are highly permeable to test substances.
B)They are defective in DNA repair and,therefore,cannot readily repair damage done by the test substances.
C)It is very straightforward to assay the conversion of their histidine auxotrophy mutations to histidine prototrophy.
D)all of the choices

Question 25

Which of the following is a possible fate for an exogenote?

A)Integration into the host chromosome.
B)Independent replication and functioning.
C)Degradation to nucleotides.
D)All of the choices.

Question 26

Which of the following is the most error-prone of the repair mechanisms?

A)postreplication repair
B)recombination repair
C)SOS repair
D)photoreactivation

Question 27

When a recipient cell acquires a piece of naked DNA from the environment,it is called

A)conjugation.
B)transformation.
C)transduction.
D)transfection.

Question 28

Repair of thymine dimers using light to split the dimers apart into separate monomers is called

A)photodedimerication.
B)photoreactivation.
C)photoreparation.
D)none of the choices

Question 29

Photoreactivation repairs thymine dimers by splitting them back into separate thymines.

Question 30

Which of these transposable elements do not carry genes for functions other than those needed for transposition?

A)insertion sequences
B)composite transposons
C)retrotransposons
D)conjugal transposons

Question 31

__________ __________ is the process by which some cells are capable of degrading an exogenote.

Question 32

In mismatch repair on newly replicated DNA,enzymes distinguish between old and newly replicated DNA strands based on the fact that newly replicated DNA strands are ________ methylated relative to older DNA.

Question 33

Transfer of genes from one mature independent organism to another is called

A)horizontal gene transfer.
B)lateral gene transfer.
C)vertical gene transfer.
D)orthogonal gene transfer.

Question 34

Approximately half of known animal carcinogens can be detected by the Ames test.

Question 35

A reciprocal exchange in which a pair of DNA with the same nucleotide sequence break and rejoin in a crossover is called __________ recombination.

A)homologous
B)site-specific
C)replicative
D)none of the choices

Question 36

The process in which one or more nucleic acid molecules are rearranged or combined to produce a new nucleotide sequence is called

A)transformation.
B)conjugation.
C)recombination.
D)transduction.

Question 37

Site-specific recombination systems

A)do not depend on extensive nucleotide sequence homology.
B)depend on enzymes that are often specific for sequences within the host.
C)are features of some viruses.
D)All of the choices are true.

Question 38

Which of the following is true of the integration of a viral genome into the host chromosome?

A)It is a form of site-specific recombination.
B)The enzymes are specific for the virus and its host.
C)Integration begins the process of host chromosome degradation.
D)It is a form of site-specific recombination and the enzymes are specific for the virus and its host.

Question 39

The Ames test

A)can be used to measure the mutagenicity of chemicals.
B)is used to measure the repair of thymine dimers.
C)is used to measure levels of oxygen free radicals.
D)none of the choices

Question 40

Alternate forms of genes resulting from mutations are called

A)isoforms.
B)alterons.
C)alleles.
D)lethal.

Question 41

Who is credited with demonstrating unidirectional and nonreciprocal transfer of DNA between two mating

A)Hayes
B)Lederberg
C)Tatum
D)none of the choices
Blooms Level: 1.Remember
Learning Outcome: 16.06.03 Outline the events that occur when an F cell encounters an F- cell
Section: 16.06
E)coli cells?

Question 42

In the mechanics of conjugation,exclusive of gene transfer,Hfr and F⁺ strains behave the same.

Question 43

In an F⁺ $\times$ F^- mating,all or part of the host chromosome usually is transferred to the recipient.

Question 44

Transposable elements have been found only in prokaryotes and do not appear to play a major role in eukaryotes.

Question 45

A recipient cell that is temporarily diploid for a portion of the genome during the replacement process is called a(n)__________.

A)merozygote
B)exogenote
C)endogenote
D)none of the choices

Question 46

Transfer of genetic information via direct cell-cell contact is called

A)transformation.
B)transduction.
C)transfection.
D)conjugation.

Question 47

In an HFR $\times$ F⁺ mating,the conjugation bridge usually breaks before chromosomal transfer is complete.Therefore,the recipient remains F^-.

Question 48

The incorporation of a single strand of donor DNA into a recipient DNA duplex so that the donor strand replaces one of the strands or the recipient duplex generates __________ DNA.

A)aberrant
B)unstable
C)heterogeneous
D)heteroduplex

Question 49

Transposons that transpose by inserting a copy at a new location while a copy remains at the original location are said to transpose by _______________ transposition.

A)simple
B)composite
C)incomplete
D)replicative

Question 50

Plasmids that have genes that decrease bacterial susceptibility to antibiotics are called __________ factors.

A)col
B)resistance
C)virulence
D)metabolic

Question 51

Insertion sequences are

A)normally relatively short (700 to 1,650 bp).
B)capable of transposition.
C)are discrete genetic elements bounded at both ends with inverted repeats.
D)all of the choices

Question 52

DNA molecules that enter a bacterium by one of several mechanisms is called a(n)

A)merozygote.
B)exogenote.
C)endogenote.
D)none of the choices

Question 53

When an F' plasmid acts as the donor in a mating,which of the following do(es)not happen?

A)The recipient becomes F'.
B)The plasmid is transferred,including the chromosomal genes now on the plasmid.
C)Some chromosomal genes not on the plasmid are transferred.
D)all of the choices

Question 54

Plasmids that have genes for pili and can transfer copies of themselves to other bacteria during conjugation are called __________ plasmids.

Question 55

The conjugation bridge in an Hfr $\times$ F^- mating usually breaks before chromosome transfer is complete; however,because at least part of the plasmid is transferred first,the recipient becomes F⁺.

Question 56

The genome of a recipient cell is called a(n)__________.

A)merozygote
B)exogenote
C)endogenote
D)none of the choices

Question 57

Conjugative transposons

A)can be transferred from one bacterium to another by a phage mediated process.
B)may be involved in the spread of antibiotic resistance in bacteria.
C)often express enzymes that degrade aromatic compounds.
D)all of the choices.

Question 58

A plasmid that can either exist independently of the chromosome or be integrated into it is called a(n)__________.

Question 59

A __________ is a piece of extrachromosomal DNA that has its own replication origin.

Question 60

Which of the following effects may be mediated by transposable elements?

A)Insertion into a gene,causing a mutation.
B)Activation of nearby genes.
C)Formation of genetic deletions.
D)All of the choices.

Question 61

Which of the following occurs with generalized transduction?

A)Degradation of the host chromosome into randomly sized fragments.
B)Packaging of any DNA fragment of the appropriate size.
C)Transfer of any bacterial gene to the subsequent host.
D)All of these occur with generalized transduction.

Question 62

Which of the following is not true of specialized transduction?

A)It is carried out by temperate phage.
B)It is restricted to those genes on either side of an integrated prophage.
C)The phage genome retains the full complement of phage genes.
D)All of these are true of specialized transduction.

Question 63

Specialized transduction can be carried out by

A)any bacteriophage.
B)any temperate bacteriophage.
C)only those temperate bacteriophages that integrate into the host chromosome.
D)all of the choices

Question 64

A __________ is a latent form of a virus genome that remains within the host without destroying it.

Question 65

Complete transfer in an Hfr $\times$ F^- mating takes approximately __________ minutes.

A)20
B)50
C)100
D)200

Question 66

Transformation has been observed in only a limited number of species in nature,but we have found ways to force the process upon other species in the laboratory.

Question 67

When an F plasmid integrates into the host chromosome,the strain is referred to as

A)F⁺.
B)Hfr.
C)F'.
D)F^-.

Question 68

In order to take up a naked DNA molecule,a cell must be __________,which may occur only at certain stages in the life cycle of the organism.

Question 69

Which of the following best represents the order of gene transfer in an Hfr $\times$ F^- mating?

A)All plasmid genes followed by some or all of the chromosome.
B)Part of the plasmid followed by the chromosome followed by the rest of the plasmid.
C)The chromosome followed by the plasmid.
D)Part of the chromosome followed by the plasmid followed by the rest of the chromosome.

Question 70

An F' plasmid results when

A)an F⁺ $\times$ F^- mating is interrupted before completion.
B)an Hfr $\times$ F^- mating is interrupted before completion.
C)an integrated F plasmid is incorrectly excised,bringing host genes with it.
D)none of the choices

Question 71

In an F⁺ $\times$ F^- conjugation,the donor is the __________ strain.

A)F⁺
B)F^-
C)both F⁺ and F^- (It is a reciprocal exchange)
D)neither F⁺ nor F^- (There is no exchange)

Question 72

After an F⁺ $\times$ F^- mating,the donor is __________ and the recipient is __________.

A)F⁺; F^-
B)F^-; F⁺
C)F^-; F^-
D)F⁺; F⁺

Question 73

The transformation frequency of very competent cells is about 10^-6,or about 1 in 1,000,000 when an excess of DNA is used.