Microbiology chp 8 Bacterial Genetics
Direct selection involves inoculating cells onto growth media on/in which
the mutant but not the parental cell type will grow.
Segments of DNA capable of moving from one area in the DNA to another are called
transposons
Following base removal, DNA polymerase can add nucleotides in the 5' to 3' direction.
true
Improper base-pairing during DNA replication causes a pause in chain elongation.
true
Match each characteristic with the appropriate nucleic acid molecule.
contains an origin of replication <-----> both plasmids and chromosomes made of double stranded RNA <-----> neither plasmids nor chromosomes typically do not encode genes essential to the life of the cell <-----> plasmids only found in all eukaryotes and prokaryotes <-----> chromosomes only
A transposon can move from the host chromosomal DNA to a plasmid.
true
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 prokaryotes, genes can be transferred from a donor to a recipient via three different mechanisms: _______, _______, and ________.
transformation conjugation transduction
Random genetic changes that result from normal cellular processes are ______.
spontaneous mutations
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
________ are circular pieces of bacterial DNA that do not usually encode information essential to the life of a cell.
Plasmids
Which mechanism of gene transfer involves the uptake of "naked" DNA by competent bacterial recipient cells?
transformation
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
The material responsible for transformation was shown to be DNA by
Avery, MacLeod, and McCarty.
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
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'
_______ 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 from outside of the cell such as radiation or chemicals.
Induced
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
Which of the following types of repair does not require the standard DNA polymerase with proofreading capability?
SOS repair
Which of the following is FALSE about transposons?
They are capable of moving independently from one cell to another cell.
_______ 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 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
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
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
Cancer-causing chemicals are called
carcinogens
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)
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
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
Two methods used to identify mutants in a culture are ______ and ______ selection.
direct; indirect
Transposons are composed of amino acids.
false
True or false: A point mutation always leads to a shift of the reading frame from the point of mutation downstream.
false
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
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
The proofreading function of DNA polymerase reduces the error rate from about one in a million base pairs to about one in a ______ base pairs.
hundred million
Chemical mutagens often act by altering the
hydrogen bonding properties of the nucleobase.
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
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
Repair of nucleotide incorporation errors during the process of DNA replication is accomplished by ________ by DNA polymerase and by ________ repair.
proofreading mismatch
A clever technique that streamlines the identification of auxotrophic mutants is
replica plating
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
Transposons are
segments of DNA
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
The mechanism by which genes are transferred into bacteria via viruses is called
transduction
The process of bacterial ________ involves the uptake of "naked" DNA by competent bacterial recipient cells.
transformation
Restriction-modification systems were discovered ______.
while studying why certain bacterial strains are relatively resistant to phage infection
DNA polymerases use their ______ activity to remove a mismatched base pair.
3' -> 5' exonuclease
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
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
In conjugation, transformation, or transduction, the recipient bacteria is most likely to accept donor DNA
from the same species of bacteria.
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 transformation transduction
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
In bacteria, _______ refers to DNA transfer requiring cell to cell contact.
conjugation
The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved
conjugation AND transposons.
The process by which organisms best adapted to a given environment will predominate in that environment is called _______.
natural selection