SmartBook Homework Assignment Chapter 8

Cancer-causing chemicals are called

Carcinogens

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

Cell death Cancer (in animals)

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

Competent

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

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

Conjugation

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

Conjugation Transduction Transformation

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

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

DNA glycosylase

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

False

True or false: Ultraviolet rays are chemical mutagens.

False

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

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

Mutation

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 of the following types of radiation are mutagenic?

Ultraviolet rays X-rays

Restriction-modification systems were discovered ______.

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

1. Contains an origin of replication 2. Made of double stranded RNA 3. Typically do not encode genes essential to the life of the cell 4. Found in all eukaryotes and prokaryotes

1. Both plasmids and chromosomes 2. Neither plasmids nor chromosomes 3. Plasmids only 4. Chromosomes only

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

DNA repair

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

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

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

True or false: A point mutation always leads to a shift of the reading frame from the point of mutation downstream.

False

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

1. Low copy number 2. High copy number 3. Narrow host range 4. Broad host range

1. Occur in one or a few copies per cell 2. Occur in many copies in a cell 3. Can replicate in only one species 4. Can replicate in many different species

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

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

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

In prokaryotes, genes can be transferred from a donor to a recipient via three different mechanisms: _____________ ,____________ , _______________ and

Bacterial transformation, Transduction, Conjugation

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

Base ; Frameshift

Which of the following are caused by chemical mutagens?

Base substitutions Frameshift mutations

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'

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

F' or F prime

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

F` or F Prime

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

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

Induced

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

Spontaneous mutations

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

Photoreactivation

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

Plasmids

CRISPR systems involve ______.

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

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

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

SOS

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

Spontaneous

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

Transduction

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

Transduction

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

Transformation

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

Transformation

Which of the following statements about transformation is correct?

Transformation is the uptake of naked DNA from the environment.

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

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

conjugation

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

Transposons

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

Transposons

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

Carcinogens; Mutagens

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

CRISPR Restriction-modification

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

Direct