Chapter 8

The consequences of not repairing damaged DNA in cells include _____

-cell death -cancer (in animals)

Mutations that are caused by external influences such as radiation or chemicals are called _____ mutations

induced

These chemicals, produced in aerobic environments, lead to the oxidation of guanine in DNA resulting in increased base substitutes

reactive oxygen species (ROS)

After new virus particles have assembled in the bacterial host cell, they are usually _____

released as a result of host cell lysis

Extensively damaged DNA activates the _____ repair mechanism, which cannot always determine the correct nucleotide sequence, thus introducing mutations resulting from the repair process itself.

SOS

Plating bacteria in duplicate patterns on both a nutrient agar plate and a glucose-salts agar is an example of _____ platting

replica

The two types of transduction are _____

specialized and generalized

Ultraviolet radiation causes a very specific type of DNA damage called ______

thymine dimers

In insertion sequences, the _____ gene (the only gene) is flanked by _____ repeats

transposase, inverted

When some species of bacteria reach a certain density or when nutrients are in short supply, they _____

turn on genes required for competence

If a scientist is working with bacteria that have typical phenotype of those isolated from nature, the bacteria are considered to be _____ type

wild

Random genetic changes that occur as a result of natural cellular processes are called _____ mutations

spontaneous

Recognition and repair of errors in nucleotide incorporation by DNA polymerase is called _____

Proofreading

In penicillin enrichment, the penicillin selects against the _____ which can grow in the medium

Prototrophs

Replica plating is a form of _____ selection in which duplicate patterns of colonies are plated onto nutrient agar and a plate with glucose-salts agar.

indirect

Which of the following are characteristics of recombinants?

-they have properties of both donor and recipient cells -they result from horizontal gene transfer

Examples of conditions where bacteria can become naturally competent in the environment include _____

-when there is a high density of bacteria -when certain nutrient are scarce

Chemical mutagens can cause which of the following?

-Base substitutions -Frameshift mutations

X rays can cause which types of damage to a DNA molecule?

-Nucleobase alterations -Single stranded breaks -double stranded breaks

Which of the following are systems bacteria can use to protect against invading DNA?

-Restriction-modification -CRISPR

The largest group of chemical mutagens consists of

Alkylating agents

_____ sometimes incorporates the incorrect nucleotide when generating a new strand of DNA during DNA: this leads to a detectable distortion in the DNA helix

DNA polymerase; replication

In humans, two of the genes associated with the development of breast cancer encode enzymes involved in _____

DNA repair

DNA transfer by conjugation is more efficient in a liquid medium setting, subjected to very mild agitation (stirring), rather than on an agar plate format. Why?

Direct cell-to-cell contact is required for this process, and this is more likely to be achieved in the fluid liquid format than on an agar plate (especially for relatively non-motile types of bacteria)

Which type of mutation alters the reading frame of a gene?

Frameshift

_____ selection is used to isolate an auxotroph from a prototrophic parent strain, because no selective medium exists to inhibit the parent

Indirect

Which is true about a crown gall tumor?

It results from the incorporation of bacterial plasmid DNA into the plant chromosome

Protection against the toxic effects of antimicrobial compounds or heavy metals is often found to be encoded on ___

R plasmids

_____ is the change of a mutated genetic sequence back to its original, non0mutated form

Reversion

The restriction-modification system always has two genes involved, the cutting enzyme and the methylating enzyme

True

When bacteriophages replicate, phage components are synthesized in the host cell and assemble into new viruses _____

Within that cell before bing released

_____ are a type of radiation that can cause single and double stranded breaks in a DNA strand

X Rays

The study of the crown gall tumor found

a bacteria plasmid promoter that was similar to plant promoters

Which of the following plasmids encodes an origin of transfer?

both conjugative and mobilizable plasmids

Unlike stranded DNA polymerase, the DNA polymerase used in SOS repair _____

can synthesize DNA even in very damaged regions

Chemicals that cause cancer are called _____

carcinogens

The general mechanisms by which most bacteria routinely respond to new circumstances are _____ change and regulating _____ expression

genetic; gene

To increase the chance of detecting carcinogens in the Ames test, the test substance is treated with

ground-up rat liver

Consider a population of bacteria susceptible to an antimicrobial. If a bacterium acquires a spontaneous mutation that gives resistance to the antimicrobial, this bacterium will _____ if the population is exposed to the antimicrobial

grow without competition

Indirect selection

is necessary to isolate auxotrophic mutants

The enzymes of the mismatch DNA repair mechanism distinguish between the template strand and the newly synthesized strand by the presence of a _____ group on certain nucleobases of the template strand

methyl

DNA is protected from restriction enzymes by being

methylated

Sometimes the proofreading function of DNA polymerase misses errors in nucleotide incorporation. These errors are usually fixed by a mechanism called _____ repair

mismatch

The genes that vary considerably among strains of a species are called the _____

mobile gene pool

Mutations are rare because _____

most damage is repaired before it is passed on to progeny

The source of variation among microorganisms that were once identical is

mutation

Chemically mutagens that modify _____ increase the odds of incorrect nucleotide incorporation during DNA replication

nucleobases

The easiest way to detect if DNA transformation occurred in the lab is if _____ grow under selective conditions

only transformed cells

Genomic islands that encode disease-causing factors such as exotoxins, capsules, and adherence factors are called _____ islands

pathogenicity

To increase the proportion of auxotrophic mutants in a population of bacteria, one may use

penicillin enrichment

The _____ is the observed characteristics of an organism

phenotype

The properties of a cell that are determined by its DNA composition are its

phenotype

Colonies of the bacterium Serratia marcescens ar red when incubated at 22C but white when incubated at 37C. This is an example of

phenotypic change

In bacterial conjugation, a donor cell with an F _____ is considered F+

plasmid

A _____ mutation occurs if a single base pair is changed during DNA synthesis

point

The designation his- refers to

the genotype of bacteria that lack a functional gene for histidine synthesis AND bacteria that are auxotrophic for histidine

The diploid character of eukaryotic cells may mask the appearance of a mutation since

the matching chromosome may carry the correct version of the gene

Errors by DNA polymerase that incorporate the wrong nucleotide into replicating DNA can be repaired quickly by which two mechanisms?

-Proofreading by DNA polymerase -Mismatch repair

Which of the following are sources of "naked" DNA?

-Secreted into the environment by bacteria -Lysed (burst) bacteria cells

Place the steps of F plasmid transfer in the correct order

1. F pilus makes contact with recipient cell 2. one strand of F plasmid is cut in origin or transfer 3. single strand of F plasmid is transferred to the recipient cell 4. complement of transferred strand is synthesized

Place the steps of DNA-mediated transformation into the correct order

1. double-stranded DNA molecule binds to surface receptor, 2. nucleases degrade one strand of double-stranded DNA at the cell surface, 3. single-stranded DNA enters cell after one strand has been degraded, 4. single-stranded DNA integrates into genome after entering the cell, 5. strand being replaced by donor DNA is degraded

The material responsible for transformation was shown to be DNA by

Avery, Macleod, and McCarty

When an excision error produces a plasmid containing both chromosomal and F plasmid DNA, the resulting plasmid is called a _____ plasmid

F'

When integrated F plasmid DNA is excised from the chromosome, an excision error can result in the removal of chromosomal DNA along with the F plasmid DNA, creating a plasmid called _____

F'

_____ are circular pieces of bacterial DNA that do not usually encode information essential to the life of a cell

Plasmids

Some bacteria have a higher incidence rate of thymine dimer mutations following exposure to UV light than others. What might be going on here to lead to this outcome?

They may simply have a higher proportion of T nucleotides next to each other in their DNA than other bacteria, leading to more possible dimers being formed AND they may have a weaker expression of photo-reactivation enzymes, leading to the formation of more thymine dimers

_____ are DNA segments that increase the rate of mutations by inserting themselves into genes and inactivating them

Transposons

_____ are segments of DNA that can move from one location to another in a cell's genome

Transposons

Crown gall is caused by a prokaryote plasmid that can be expressed in plant cells.

True

DNA polymerase is able to proofread the DNA sequence

True

Each gene mutates at a characteristic frequency.

True

Because CRISPR systems involve bacteria using retained segments of DNA to identify and destroy future invading phage DNA, these systems are a form of _____

adaptive immunity

Chemicals called _____ add alkyl groups onto nucleobases, changing their base-pairing properties.

alkylating agents

Base _____ structurally resemble nuclebases and can be mistakenly incorporated into nucleotides and then into DNA

analogs

Many bacteria are able to recognize and destroy invading DNA. It is thought this ability evolved _____

as defenses against phages

A mutant that requires a growth factor is an _____

auxotroph

in replica plating, colonies that grow on the master plate but cannot grow on the glucose-salts plate are _____

auxotrophs

Modified nucleobases can result in _____ if they are not repaired before DNA replication occurs

base substitutions

Conjugation, DNA-mediated _____, and _____ are methods of horizontal gene transfer in bacteria

transformation; transduction

Variation in the color of corn kettles, as described by Dr. Barbara McClintock, is an example of the process called _____

transposition

Segments of DNA capable of moving from one area in the DNA to another are called

transposons

On which of the following DNA strands would UV radiation have the most effect?

AATTAGTTC

Which change in a gene's DNA sequence would have the least effect on the eventual amino acid sequence produced from it?

Addition or deletion of three consecutive nucleotides

You mix two bacterial stains in a tube of glucose-salts agar. One strain is His-, Val-, while the other strain is Trp-, Leu-. You previously showed that neither strains grows on glucose-salts agar. After incubating the tube, you plate a sample onto a new glucose-salts agar plate. Several new colonies grow. What do you know is TRUE about these colonies.

The bacteria in the colonies are His+, Val+, Trp+, Leu+

A bacterial strain is resistant to infection by a bacteriophage. which statement is FALSE

The bacterial host DNA is protected from restriction enzyme degradation by phosphorylation

DNase is added to a mixture of donor DNA and recipient. If the donor DNA is naked, what will happen?

The recipient will be unable to acquire DNA via transformation

_____ such as E. coli are an excellent model system for genetics studies because they can quickly grow to high densities, allowing us to screen for rare genetic events

bacteria

A bacterial cell described as _____ can take up DNA from the surrounding environment

competent

not all bacteria can take up DNA from the environment. Those that can are referred to as

competent

in bacteria, _____ refers to DNA transfer requiring cell to cell contact

conjugation

Mutants that can grow under conditions, in which the parent (wild type) cells cannot, are easily isolated by _____ selection

direct

Mutant cells in bacterial cultures can be isolated by _____ and _____ selection methods

direct and indirect

In conjugation, transformation, or transduction, the recipient bacteria is most likely to accept donor DNA

from the same species of bacteria

Bacteria that have properties of both the donor and recipient cells are the result of

genetic recombination

DNA repair mechanisms occur

in both eukaryotes and prokaryotes

In the Ames test, it is expected that a mutagen would _____ the reversion rate of a histidine-requiring auxotroph of Salmonella

increase

The clustered, regularly interspaced short palindromic repeats (CRISPR) system in bacterial cells has been called the "immune" system of bacteria. CRISPR protect bacteria from a repeat infection from the same phage because bacterial cells

integrate fragments from the phage DNA in their own chromosomes and target for destruction any DNA that contains the same fragments in the future

Chemical mutagens that squeeze between base pairs and induce frameshift mutations are called _____

intercalating agents

Among the easiest of the mutations to isolate are those which

involve haploid chromosomes AND involve antibiotic resistance

Genetic change in bacteria occurs through which two mechanisms?

-horizontal gene transfer -mutation

What are some of the disadvantages of the SOS DNA polymerase?

-it. can result in a lot of mutations in the DNA -it has no proofreading ability

Some prokaryotes are naturally competent _____

-only under specific conditions -all the time

A bacteriophage consists of what two major components?

-protein coat -DNA or RNA genome