mastering micro ch.10
At which point does a recipient cell become an F+ cell? 1. Fusion of the cell membranes 2. Attachment of the sex pilus 3. Transfer of the single stranded F factor 4. Pulling of donor and recipient cells together 5. Formation of the complementary strand of the F factor
5. Formation of the complementary strand of the f factor
Which of the following is a characteristic of an F+ cell?
Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell.
Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains?
Conjugation is typically disrupted before the fertility factor can be transferred.
Which of the following attaches the target gene to a desired location?
DNA ligase
F+ strains of Escherichia coli have
F factor plasmid
What is required by an F- cell to become an F+ cell?
F plasmid
How is generalized transduction different from specialized transduction?
Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.
How does an F+ cell differ from an Hfr cell?
Hfr strains have the F plasmid integrated into the chromosome.
What benefit does the F- strain receive from mating with an Hfr strain?
It acquires new, potentially beneficial genes from the Hfr strain.
Why would a recombinant DNA molecule be inserted into a host cell?
It can be copied, transcribed, and translated into a desired protein.
What describes how 5-bromouracil might create a mutation?
It can replace the base thymine, and can base pair with guanine rather than adenine
What is the function of the conjugation pilus?
It pulls the F+ and F- cells together.
Which finding is most surprising from Griffith's experiments?
S strain cells are isolated from the blood of mice infected with heat-killed S strains and live R strains.
What most likely explains the recovery of live S strain cells from a mouse injected with heat-killed S strain mixed with live R strain cells?
The R strain picked up the S strain DNA, enabling it to produce a capsule.
What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell?
The host DNA integrates, with the prophage, into the new recipient chromosome.
How does specialized transduction differ from regular lysogeny?
The prophage in specialized transduction carries with it pieces of the host chromosomal DNA.
How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population?
The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
In general, how might recombinant DNA technology be used to prevent a genetic disorder caused by a mutation in a single gene?
To insert a desirable gene, remove an undesirable gene, or replace a defective gene with a functioning gene
What is unique about transduction compared to normal bacteriophage infection?
Transduction transfers DNA from the chromosome of one cell to another.
ionizing radiation does not include
UV rays
A "point mutation" refers to mutations involving
a substitution, deletion, or addition of one base-pair.
A nucleotide-altering chemical can
alter nitrogenous bases of DNA, resulting in incorrect base pairing
What is the key difference between donor cells and recipient cells?
an F plasmid (F+ & F- plasmid)
A mutant that has a nutritional requirement for growth is an example of a(n)
auxotroph
What might result from a frameshift mutation?
benzopyrene
Competent cells are cells that
can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination.
F- strains of Escherichia coli
do not have an F factor.
Microinsertions and microdeletions often result in ________ mutations.
frameshift
What increases the likelihood of mutations in DNA?
mutagens
Thymine Dimers result from
non-ionizing radiation (UV light)
What cellular macromolecule is the fertility factor comprised of?
nucleic acid
The mutagens 2-aminopurine and 5-bromouracil are examples of
nucleotide base analogs
The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA.
pili
A plasmid may
replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.
Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?
silent mutation
Mice that are injected with only the R strain of Streptococcus pneumoniae
stay healthy, because their immune systems can kill this strain easily.
When a transducing phage interacts with a new host cell
the DNA from the previous host can recombine with the new host chromosome.
What characteristic of the S strain allows it to evade the immune system of the mice?
the cells have a capsule
The killing of cells by UV irradiation involves
the formation of pyrimidine dimers
How do restriction enzymes cut DNA sequences?
they cut DNA at sites called recognition sites, that have specific nucleotide sequences
contains fragments of the host chromosome instead of the viral genome.
transducing phage
Which of the following methods may introduce foreign DNA into a recipient?
transformation, transduction, and conjugation
The uptake of DNA released from a cell is ________, while transfer of DNA with cell-to-cell contact would most likely result in ________.
transformation/conjugation
[t/f] Almost all plasmids are double-stranded DNA.
true
[t/f] Intercalating agents, like acridine orange and ethidium bromide, lead to mutagenesis by pushing DNA base pairs apart, which can lead to insertions or deletions.
true
[t/f] Most plasmids are circular rather than linear.
true