chapter 8 review
Transposons can cause mutations by
"jumping" into a gene and disrupting its function.
After the transfer of the F plasmid is complete
F- cell becomes F+
Mismatch repair is activated by
any difference between the nucleotide sequence in the donor and recipient DNAs.
A virus that infects bacterial cells is called a ______.
bacteriophage
Match the chemical mutagens with their descriptions.
base analogs- used in place of normal nucelobases transposons- randomly insert into DNA alkylating agents- add CH3 and others to nucleobases intercalating agents- insert between base pairs
After entry of the bacteriophage into the host cell, a phage enzyme
breaks the host DNA into fragments
When the bacteriophage transfers bacterial DNA into a recipient bacterial cell, that DNA
can integrate into the chromosome
Consider the figure below and check all the TRUE statements.
- A vancomycin-resistant S. aureus mutant is created. - In order for S. aureus to become vancomycin-resistant, conjugation must have occurred between the E. faecalis and the S. aureus. - Either the S. aureus or the E. faecalis must have a conjugative plasmid.
Which of the following genes are likely to be found on a plasmid rather than on the bacterial chromosome?
- BT toxin gene - chloramphenicol-resistance gene - oil degradation enzyme genes
Which of the following is/are true about CRISPR? (NOTE: Please change all question marks to checkmarks for correct
- CRISPR loci can reveal a historical record of phage infections of a bacterial cell. - CRISPR systems act as a barrier to horizontal gene transfer.
consider the figure below. which statement is true
5- bromouracil may be incorporated into a newly synthesized DNA strand in place of thymine nuclease
On which of the following DNA strands will UV light have the most effect?
ACTTGCTTAC
Which of the following is FALSE about transposons?
They are capable of moving independently from one cell to another cell.
Generalized transduction occurs when
a bacteriophage packages a piece of bacterial DNA during replication
During maturation or formation of phage particles
a few phage heads may surround fragments of host bacterial DNA
A "nosocomial" infection is an infection acquired through
a hospital stay
which of the following statements regarding mutations is TRUE
a phototroph can grow on glucose-salts media
the F pilus is
a protein appendage that attaches the two cells
Based upon information in Chapter 8 and the case study, it appears that multidrug resistant strains of bacteria such as A. baumannii:
acquired their resistance genes from other bacteria in healthcare facilities.
cinetobacter baumannii may have acquired resistance to multiple antibiotics through
all of these (transformation, conjunction, transduction)
The plasmid is mobilized for transfer when
an endonuclease cleaves it at the origin of transfer
The basic parts of a bacteriophage are
an icosohedral head, central tube, tail pins, and fibers
A. baumannii is easily removed from hospital surfaces by disinfectants.
false
Nosocomial infections caused by A. baumannii in civilian hospitals are not a major concern.
false
A culture of E. coli is irradiated with UV light. The UV light affects the cell's DNA by
forming covalent bonds between thymine bases on the same strand of DNA.
During the process of transformation in the lab setting, cells are plated on selective media to
make sure that only transform ants grow
Genes from the donor chromosome are transferred as
single stranded DNA
In transformation, genes from a donor chromosome are transferred as
single-stranded DNA
During conjugation, the donor chromosome is transferred as
single=stranded DNA
Acinetobacter baumannii is a common resident of ____
soil and water
Infections caused by A. baumannii have most frequently been seen in
soldiers at military hospitals
the F pilus binds to
specific receptors on the cell wall of the recipient
the F plasmid encodes for
the F pilus
After the conjugation of an Hfr cell with an F- cell,
the recipient remains f-
Two bacterial genes are transduced simultaneously. What does this suggest about the location of the two genes relative to each other?
the two genes must be close together on the bacterial chromosome.
The main advantage for bacteria that have the ability to carry out conjugation and other forms of genetic exchange is that
they become genetically diverse
Preventing the function of light repair (photoreactivation) interferes with the repair of which of the following?
thymine dimers
The donor cell DNA is integrated into the recipient cell's DNA by homologous recombination.
true
plasmids are
able to replicate independently of the chromosome
Transformation is facilitated by
proteins on the cell wall that bind DNA
if you find that a particular plasmid has an R factor, the bacteria that has it will be
resistant to certain antibiotics
Match each mechanism of resisting phage infection with its description.
restriction-modification systems- modifying self-DNA shortly after it's produced, followed by using restrictions endonuclease to digest DNA that lacks modification CRISPR system- insertion of small fragments of phage genome into host chromosomes, giving the cell a "memory" of previous attempted infection and a way to recognize and destroy that foreign DNA in the future preventing phage attachment- changing or covering up molecules on the surface of the bacterium to which the phage particle binds
DNA polymerases use their ______ activity to remove a mismatched base pair.
3'-> 5' exonuclease
The researcher inoculates the test population of bacteria onto glucose salts agar containing penicillin and also on nutrient agar containing penicillin. She counts 25 colonies on the glucose salts plate lacking histidine and 32 colonies on the nutrient agar. Which of the following statements is TRUE?
- The colonies on both plates contain penicillin-resistant mutants. - The glucose salts plate contains some mutants.
Place the following events in the process of virus replication and the generation of a transducing particle in the correct order.
- a bacteriophage attaches to a specific receptor on a host cell - phage DNA enters the bacterial cell. the empty phage coat remains outside the host cell - enzymes coded for by the phage cut the bacterial DNA into small pieces - phage nucleic acid is replicated and coat proteins are synthesized - during virus assembly, bacterial DNA can sometimes mistakenly be packaged in the protein coat, creating a transduction particle
which of the following statements regarding bacterial genetics is/are TRUE
- a change in genotype can change the phenotype -an auxotroph has different genotype than a phototroph - an auxotroph has a different phenotype than a photo trough
Place the correct sequence of experiments in order to better understand the Griffith Experiment for Transformation.
- living encapsulated cells - living non-encapsulated cells/ heat-killed encapsulated cells - heat killed encapsulated cells/ living non-encapsulated cells
Examples of advantageous genes that can be transferred by transduction are genes for
- sugar fermentation. - toxin production. - drug resistance. - only drug resistance and toxin production. - All of these.
Consider the figure and check the CORRECT statements. (NOTE: Please change all question marks to checkmarks for correct answers or empty boxes for incorrect answers.)
- the nucelobase shown in yellow should be a C - The CH3 groups alert the mismatch repair system to which DNA strand is the template strand. - Without the CH3 groups, it is possible that the mismatch repair system would replace the G nucleobase (purple arrow) with an A.
Consider the figure. If methylguanine replaces guanine in a DNA strand with the sequence 5'CGA3', the resulting change in the complementary strand after DNA replication would be
3'GTT5'
Repair mechanisms that occur during DNA synthesis are 1. mismatch repair 2. proofreading by DNA polymerase 3. light repair 4. excision repair 5. SOS repair
1 and 2
Match the mutation with the correct name. Not all labels are used.
1. Wild type 2. silent mutation 3. missense mutation 4. nonsense mutation 5. outcome
Place the following events in the process of transduction in the correct order. Not all labels are used.
1. a transfusing particle attaches to a specific receptor on a host cell 2. bacterial DNA is injected into a cell 3. foreign bacterial DNA integrates into the host genome by homologous recombination 4. bacteria multiply with new genetic material
Which is the correct labeling of the mutations in the figure?
1: silent; 2. nonsense; 3. missense
Which of the following statements about the Ames test is FALSE?
Liver extract is added to provide nutrients.
Please match each type of mutation with its appropriate description.
Nonsense mutation- a mutation that changes a codon that specifies an amino acid to a stop codon, resulting in premature termination of polypeptide synthesis minssense mutation- a mutation that results in changing a codon such that a different amino acid is specified - silent mutation- a mutation that changes a codon into a different codon, but both codons specify the same amino acid; this causes no change in resulting polypeptide frameshift mutation- a mutation resulting from an insertion or deletion of bases that cause a change in the reading frame of the mRNA
which of the following types of repair does not require the strand DNA polymerase with proofreading capability
SOS repair
Consider the figure below, showing repair of DNA. Which statement about the process is TRUE?
The enzymes involved in the process are DNA degrading enzyme, DNA polymerase and DNA ligase.
As a result of mismatch repair during transformation:
cells may have either original DNA or donor DNA in them.
Cells that are capable of bringing DNA from their environment into the cell through their cell wall are ______.
competent
horizontal gene transfer can occur via
conjugation
In addition to transformation, the other two forms of horizontal gene transfer are
conjugation and transduction
Because all of the genes coding for antibiotic resistance have been found to come from other organisms, A. baumannii most likely acquired them through
conjugation or a similar process of genetic exchange.
the 1st step in conjugation is
contact between the donor and recipient.
acterial 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
In the beginning of transformation, ______ binds to the target cell.
double-stranded DNA
Transformation is a form of horizontal gene transfer that involves homologous recombination. Homologous recombination is
genetic recombination between similar or identical nucleotide sequences
The classic transformation experiment done by Griffith used
harmless and virulent strains of Streptococcus pneumoniae.
f+ cells
have a plasmid and are donors in conjugation.
plasmid DNA is transferred
in single-stranded form
In transduction, bacterial DNA is transferred to a new cell when
it is injected by the virus carrying bacterial DNA
Consider the figure. If the purple liquid was distilled water, the researcher would expect the number of colonies on plate A to be _____ as the number on plate B.
more or less the same
If Gene X codes for an F pilus and transposition occurs, then the bacterium containing the plasmid would
no longer be able to conjugate
During the entry of the donor DNA into the recipient cell
one strand is broken down by nucleases
a recombinant organism is
one that contains genes from another organism
Bacteriophages adsorb or attach
only to members of the same bacterial species
the donor DNA
pairs with a homologous region of the recipient DNA.
If a Gram-positive competent cell takes up DNA containing a penicillin resistance gene, what would be added to a selective medium to isolate the transformants?
penicillin
To isolate penicillin-resistant mutants, the scientist must inoculate the parent population on plates containing ______; this approach is ______ selection.
penicillin; direct
After host cell DNA is broken down by a viral enzyme,
phage DNA is replicated and phage coat proteins are produced
A difference between transferring plasmids and DNA fragments between bacterial cells is
plasmids can replicate independently