SmartBook Homework Assignment Chapter 8

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

_______ is the transfer of bacterial DNA from a donor to recipient via a bacteriophage.

Transduction

Which of the following statements about transformation is correct?

Transformation is the uptake of naked DNA from the environment.

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

Transposons

Which of the following types of radiation are mutagenic?

Ultraviolet rays X-rays

In conjugation in E. coli, an Hfr cell refers to ______.

a cell in which the F plasmid has been integrated into the cell chromosome

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

competent

Cells that have the ability to take up DNA from the environment are called ______ cells.

competent

In bacteria, ________________ refers to DNA transfer requiring cell to cell contact.

conjugation

The F or fertility plasmid contains genes that are required for bacterial ______.

conjugation

A plasmid that can directs its own transfer from donor to recipient cells is called a(n) ________________ plasmid.

conjugative

Conjugation in bacteria requires ______.

contact between donor and recipient cell

In E. coli, less than 50% of the genes are found in all strains. These conserved genes are called the ________________ genome.

core

The genes that are present in all strains of a given species are called the ______.

core genome

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

direct

Selecting penicillin-resistant mutants by plating them on a medium containing penicillin is an example of ______ selection.

direct

An auxotroph can be isolated from a prototrophic parent strain by ______ selection.

indirect

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

indirect

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

induced

Plasmids with a _______________ copy number occur in only one copy per cell, while those with a ____________________ copy number are present in many copies per cell.

low high

Repair of nucleotide incorporation errors during the process of DNA replication is accomplished by _____________ by DNA polymerase and by ________________ repair.

proofreading mismatch

Which of the following are the three main methods of gene transfer in bacteria?

transformation conjugation transduction

In prokaryotes, genes can be transferred from a donor to a recipient via three different mechanisms: _____________________, ________________________. and ____________________.

transformation transduction conjugation

Mutagens that are DNA segments that can insert into genes and thereby inactivate them are called ______.

transposons

Segments of DNA that can move to new positions within the genome of a single cell are called ________________.

transposons

A point mutation always leads to a shift of the reading frame from the point of mutation downstream.

False

In bacterial conjugation, all F+ donor cells are high frequency recombinant (Hfr) cells.

False

Ultraviolet rays are chemical mutagens.

False

Match each characteristic with the appropriate nucleic acid molecule. contains an origin of replication made of double stranded RNA typically do not encode genes essential to the life of the cell found in all eukaryotes and prokaryotes

both plasmids and chromosomes neither plasmids nor chromosomes plasmids onlyf chromosomes only

The process of bacterial __________________ involves the uptake of "naked" DNA by competent bacterial recipient cells.

transformation

A(n) _________________ is a change in the nucleotide sequence of DNA that is passed on to daughter cells.

mutation

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

restriction-modification CRISPR

CRISPR systems involve ______.

retained segments of phage DNA used by bacteria to recognize and destroy future invading DNA

The mechanism by which bacterial DNA is moved from one bacterium to another by a bacteriophage is called __________________.

transduction

Restriction-modification systems were discovered ______.

while studying why certain bacterial strains are relatively resistant to phage infection

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

Mismatch repair Proofreading by DNA polymerase

Please match the statements about plasmid properties with the correct definition. Low copy number High copy number Narrow host range Broad host range

Occur in one or a few copies per cell Occur in many copies in a cell Can replicate in only one species Can replicate in many different species

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

Plasmids

Genetic change in bacteria occurs through which two mechanisms?

mutation horizontal gene transfer

Organisms most fit to survive in a given environment will predominate because they can reproduce more rapidly than others. This phenomenon is called _______________ ________________.

natural selection

The process by which organisms best adapted to a given environment will predominate in that environment is called _______.

natural selection

Which type of DNA repair is shown in this figure?

nucleotide excision repair

This figure shows the steps of ______, a process that repairs thymine dimers by breaking the covalent bonds that have formed between adjacent thymines.

photoreactivation

This image highlights a bacterial defense against invading bacteria called the ___________________-_________________ system.

Restriction-Modification

During repair of oxidized guanine, which enzyme removes the damaged nucleobase from the sugar-phosphate backbone?

DNA glycosylase

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

DNA repair

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

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

as a defense against phages

Chemical mutagens can cause two types of mutations: ____________ substitutions and _______________ mutations.

base frameshift

The type of DNA damage repair illustrated here is _______.

base excision repair

Cancer-causing chemicals are called ___________.

carcinogens

A(n) ______________ mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation downstream.

frameshift

A(n) ________________ mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation downstream.

frameshift

Which of the following are caused by chemical mutagens?

frameshift mutations base substitutions

Mutations that arise naturally during cellular metabolism, and not as a result of exposure to mutation-causing agents, are called ________________ mutations.

spontaneous

Random genetic changes that result from normal cellular processes are ______.

spontaneous mutations

Base ______ mutations occur when an incorrect nucleotide is incorporated in place of another during DNA synthesis.

substitution

The most common type of mutation is base ______________, where an incorrect nucleotide is incorporated during DNA replication.

substitution

The genetic transfer mechanism shown here is called

transformation

Mutant cells in bacterial cultures can be isolated by ______________ selection and _______________ selection methods.

direct indirect

Two methods used to identify mutants in a culture are ______ and ______ selection.

direct; indirect

When an excision errors produces a plasmid containing both chromosomal and F plasmid DNA, the resulting plasmid is called a(n) ____________________ plasmid.

F'

When integrated F plasmid DNA in an Hfr cell 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'

___________________ mutations are genetic changes caused by factors from outside of the cell such as radiation or chemicals.

Induced

______ repair is activated by extensive DNA damage and uses a polymerase that lacks proofreading ability, ultimately resulting in mutations.

SOS

Which mechanism of gene transfer involves the uptake of "naked" DNA by competent bacterial recipient cells?

Transformation

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

Transposons

Chemicals that cause cancer are known as ______, and most of them are ______.

carcinogens; mutagens

The consequences of not repairing damaged DNA in cells include ______.

cell death cancer (in animals)

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

Plasmids