Human Pathogens Chapter 8

T/F: A missense mutation has a greater impact on a cell than does a frameshift mutation.

false

T/F: Ultraviolet rays are chemical mutagens.

false

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

indirect

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

induced

Genetic change in bacteria occurs through who two organisms?

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

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

proofreading by DNA polymerase mismatch repair

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 mutation

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

substitutions

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

substitutions

The mechanisms 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 a recipient via bacteriophage.

transduction

The process of bacterial ___ involves the uptake of "naked" DNA by competent bacterial cells

transformation

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

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

SOS

Which of the following are caused by chemical mutagens?

base substitutions frameshift mutations

Chemical mutagens can cause two types of mutations: ___ substitutions and ___ mutations

base; frameshift

Cancer causing chemicals are called

carcinogens

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

competent

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

competent

The F of fertility plasmid contains genes that are required for bacterial ___

conjugation

A plasmid that can direct its own transfer from donor to recipient cells is called a(n) ___ plasmid

conjugative

Conjugation in bacteria requires

contact between donor and recipient cell

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

direct

Which of the following types of radiation are mutagenic?

x-rays; ultraviolet rays

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

SOS

Which of the following statements about transformation is correct?

Transformation is the uptake of naked DNA from the environment

In conjugation in E. coli, and Hfr refers to

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

The consequences of not repairing damaged DNA in cells include

cancer (in animals) cell death

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

carcinogens; mutagens

Horizontal gene transfer can occur via

conjugation

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

conjugation

Which of the following best describes vertical gene transfer?

copying parts of the genome and passing them to a daughter cell via a bacteriophage

Bacterial cells that have been genetically modified to carry an antibiotic resistance gene can be separated from susceptible (non-resistant) microbes by using a ___ selection method using agar plates with antibiotic

direct

Selecting penicillin-resistant mutants by planting 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

T/F: A point mutation always leads to a shift of the reading frame from the point of mutation downstream.

false

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

false

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

frameshift

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

indirect

___ mutations are genetic changes caused by factors form outside of the cell such as radiation or chemicals

induced

Which of the following types of repair does not require the standard DNA polymerase with proofreading capability?

light repair

Repair mechanisms that occur during DNA synthesis are:

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

The source of variation among microorganisms that were once identical is

mutation

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

natural selection

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

proofreading; mismatch

Indirect selection methods used to identify possible carcinogens (ex: Ames testing), what does it mean when a chemical can cause a bacterium to develop resistance to some environmental condition?

the chemical is a mutagen

Direct selection involves inoculating cells onto growth media on/which

the mutant but not the parental cell type will grow

Irradiation of cells with ultraviolet light may cause

thymine dimers

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

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

transposons

In prokaryotes, genes can be transferred from a donor to a recipient via three different mechanisms 1. 2. 3.

1. transformation 2. transduction 3. conjugation

On which of the following DNA strands will UV light have the most effect?

?

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 involves in ___

DNA repair

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

F Prime

When integrated F plasmid DNA is an Hfr 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'