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'