ENVS 2126: Practice ass#8 (Slawomir Lomnicki)
Which of the following features are common to transformation, transduction, and conjugation? (1) unidirectional transfer of genes (2) incomplete gene transfer (3) homologous recombination (4) meiosis occurring in the recipient -1,2 -1,2,3 -1,2,4 -3,4
1, 2, 3
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
what is transferred during bacterial conjugation? -A bacterial plasmid -A bacterial chromosome -RNA -A conjugation pilus
A bacterial plasmid
Insertion sequences target which areas on a target DNA sequence? -A sequence of nucleotides identical to the inverted repeat sequence found on the insertion sequence itself -A gene coding for antibiotic resistance -The gene that codes for transposase -A unique inverted repeat sequence not found on the insertion sequence
A sequence of nucleotides identical to the inverted repeat sequence found on the insertion sequence itself
Consider conjugation in Escherichia coli. In which of the following matings would chromosomal genes be transferred most frequently? F+ x F+ F+ × F- Hfr × F- F- × F-
Hfr × F-
Which of the following is a characteristic of an F+ cell? -Ability to synthesize sex pili -Presence of a fertility factor -Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell. -Ability to mate with an F- cell
Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell
Homologous recombination has been observed in -Eukarya. -Bacteria. -Archaea. -All three domains (Archaea, Bacteria, and Eukarya).
All three domains (Archaea, Bacteria, and Eukarya).
What is the key difference between donor cells and recipient cells? -A chromosome -Size -Cell membranes -An F plasmid
An F plasmid
Which of the following might result in a frameshift mutation? -Benzopyrene -5-bromouracil -Nitrous acid
Benzopyrene
Which type of transposon would contain a gene for transposase? -Both simple and complex transposons -Simple transposons -Neither simple nor complex transposons; the transposase enzyme is coded independently by the cell. -Complex transposons
Both simple and complex transposons
What is one of the changes that occur when a cell contains an F plasmid that is NOT integrated into the chromosome? -It is no longer able to produce a pilus. -Mutation rates are decreased. -Cell surface receptors change, preventing the uptake of more plasmids through conjugation. -The cell is considered an Hfr cell.
Cell surface receptors change, preventing the uptake of more plasmids through conjugation
How do complex transposons differ from simple transposons? -Complex transposons are found in multiple locations in the target DNA; simple transposons are found only in one location. -Complex transposons code for transposase; simple transposons do not. -Complex transposons code for additional genetic elements, such as antibiotic resistance genes; simple transposons only code for the transposase gene essential for the tranposon itself.
Complex transposons code for additional genetic elements, such as antibiotic resistance genes; simple transposons only code for the transposase gene essential for the tranposon itself.
Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate? -It does not require two cells to occur. -Sex is a phenomenon only seen in animals. -Bacteria are neither male nor female. -Conjugation does not result in the formation of new offspring.
Conjugation does not result in the formation of new offspring
Which statement about conjugation is false? -After conjugation, each cell involved has a copy of the shared DNA. -Conjugation is a process of bacterial reproduction. -E. coli is the model for bacterial conjugation.
Conjugation is a process of bacterial reproduction
Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains? -The cell membranes between the two strands never fuse together. -Conjugation is typically disrupted before the fertility factor can be transferred. -Hfr strains lack fertility factor. -The transferred genes typically recombine with the recipient chromosome.
Conjugation is typically disrupted before the fertility factor can be transferred
The SOS regulatory system is activated by -transcription of LexA. -repression of RecA. -the activity of DNA polymerase IV. -DNA damage.
DNA damage
Which of the following attaches the target gene to a desired location? -Chromosomal DNA -Plasmids -DNA ligase -Restriction enzymes
DNA ligase
What is required by an F- cell to become an F+ cell? - F plasmid - F+ chromosome -Conjugation pilus -An F- cell to be a recipient
F plasmid
How is generalized transduction different from specialized transduction? -Only one specific host gene is transferred in both specialized transduction and generalized transduction. -Specialized transduction uses animal viruses instead of bacteriophage. -Generalized transduction is initiated by a lysogenic bacteriophage; specialized transduction is initiated by a lytic phage. -Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.
Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage.
Which of the following is most similar to lysogeny? -F+ state -F state -F- state -Hfr state
Hfr state
How does an F+ cell differ from an Hfr cell? -Hfr strains have the F plasmid integrated into the chromosome. -Hfr strains can no longer reproduce. -Hfr cells cannot perform conjugation. -F+ cells have no plasmids.
Hfr strains have the F plasmid integrated into the chromosome
How would you be able to determine if the Tn5 transposon you put into a bacterium integrated into the host genome? -The cells would grow at a faster rate than without the transposon. -If the Tn5 transposon integrated into the host genome, the cells would show resistance to the antibiotic kanamycin. -The cells would become longer due to the extra DNA in them. -If the Tn5 transposon integrated into the host genome, the cells would not be able to take in any new tranposons.
If the Tn5 transposon integrated into the host genome, the cells would show resistance to the antibiotic kanamycin
Mutation rates are similar in Bacteria and Archaea, yet certain stressful conditions mutation rates increase. Why is the mutation rate not constant and close to zero all of the time? -Constant mutation rates would halt evolution completely. -Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival. -Microorganisms carefully control the mutation rate of their DNA to match the environmental conditions and maximize evolution. -The increased mutation rate under stressful conditions is an indication that the microorganisms can no longer replicate their DNA properly and are about to die.
Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival.
What benefit does the F- strain receive from mating with an Hfr strain? -It can now produce sex pili. -It becomes an F+ cell. -It acquires new, potentially beneficial genes from the Hfr strain. -It picks up a fertility factor.
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. -It can protect the recombinant DNA. -Restriction enzymes can only be used inside of a cell. -Plasmids cannot be isolated outside of a host cell.
It can be copied, transcribed, and translated into a desired protein
Which of the following describes how 5-bromouracil might create a mutation? -It can form thymine dimers. -It can replace the base thymine, and can base pair with guanine rather than adenine. -It causes double-stranded breaks of the DNA. -it creates bulges in the DNA that must be repaired.
It can replace the base thymine, and can base pair with guanine rather than adenine
Why does a complex transposon often contain an extra piece of DNA between the two insertion elements? -It prevents degradation of the whole transposon. -It is often a gene that confers a survival advantage to the host, such as antibiotic resistance. -The insertion elements require a certain distance between them to function properly.
It is often a gene that confers a survival advantage to the host, such as antibiotic resistance.
What is the function of the conjugation pilus? -It pulls the F+ and F- cells together. -It contains an F plasmid. -It converts F- cells into F+ cells. -It carries the chromosome of F- cells.
It pulls the F+ and F- cells together
Which of the following is TRUE of natural competence? -It commonly occurs with high efficiency in nature. -It requires special proteins such as a cell wall autolysin. -It cannot occur naturally in bacteria. -It is not required for transformation.
It requires special proteins such as a cell wall autolysin
Which of the following repair mechanism(s) does not involve DNA polymerase? -Light-repair mechanism -Excision-repair mechanism -Mismatch-repair mechanism
Light-repair mechanism
Lysogeny probably carries a strong selective advantage for the host cell because it... - confers resistance to infection by viruses of a different type (or strain). - confers resistance to infection by many virus types and prevent cell lysis. -confers resistance to infection by viruses of the same type.prevents cell lysis.
Lysogeny probably carries a strong selective advantage for the host cell because it... - confers resistance to infection by viruses of a different type (or strain). - confers resistance to infection by many virus types and prevent cell lysis. -confers resistance to infection by viruses of the same type. -prevents cell lysis.
Which of the following repair enzymes cannot repair thymine dimers? -Mismatch-repair enzymes -Light-repair enzymes -Excision-repair enzymes
Mismatch-repair enzymes
What cellular macromolecule is the fertility factor comprised of? -Carbohydrate -Lipid -Nucleic acid -Protein
Nucleic acid
Transformation and homologous recombination allow for the formation of heteroduplex DNA. Which of the following would occur during DNA replication of this molecule? -Both daughter strands are complementary to the parent DNA molecule. -One daughter strand is complementary to the recombinant DNA molecule, while the other daughter strand is complementary to the parent DNA molecule. -Both daughter strands are complementary to the recombinant DNA molecule. -None of the answers are correct.
One daughter strand is complementary to the recombinant DNA molecule, while the other daughter strand is complementary to the parent DNA molecule.
How does replicative transposition differ from cut-and-paste transposition? -Replicative transposition integrates into the host genome; cut-and-paste transposition does not. -Replicative transposition results in the transposon being copied to a new location; in cut-and-paste transposition, the entire transposon moves to the new location. -Replicative transposition is faster than cut-and-paste transposition. -Replicative transposition makes use of the enzyme transposase; cut-and-paste transposition does not.
Replicative transposition results in the transposon being copied to a new location; in cut-and-paste transposition, the entire transposon moves to the new location
What must occur for bacterial conjugation to take place? -The cells must come into contact with each other. -Each cell must contain a plasmid. -The cells must transfer RNA. -One of the cells must be E. coli.
The cells must come into contact with each other
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. -The DNA is chewed up by enzymes found in the recipient cell. -The DNA begins to replicate without integrating into the host chromosome.
The host DNA integrates, with the prophage, into the new recipient chromosome.
If the gene that codes for transposase is mutated so that it no longer produces the fully functional enzyme, how will the insertion sequence be affected? -Nothing; the transposase gene has no known role for mobilizing insertion sequences. -The insertion sequence would randomly insert itself into new locations in the DNA. -The transposase enzyme would cut randomly in the host genome, effectively killing the cell. -The insertion sequence would lose its ability to effect its own movement.
The insertion sequence would lose its ability to effect its own movement.
Why is light required for photolyases? -Light excises the section of DNA to be repaired. -The light helps identify the damaged strands. -Light is used to activate the DNA polymerase to repair the gap. -The light provides the energy to break the bonds between the thymine dimers.
The light provides the energy to break the bonds between the thymine dimers.
How is DNA methylation used in DNA repair? -The mismatch-repair enzymes can use a lack of methylation to identify and remove newly synthesized DNA. -Methyl groups are required to cut DNA. -Methyl groups activate photolyases in light-repair. -Methyl groups identify thymine dimers in the DNA.
The mismatch-repair enzymes can use a lack of methylation to identify and remove newly synthesized DNA
How does specialized transduction differ from regular lysogeny? -The prophage is not excised during specialized transduction. -The resulting bacteriophage from specialized transduction does not contain any viral DNA. -The prophage in specialized transduction carries with it pieces of the host chromosomal DNA. -The resulting bacteriophage from specialized transduction cannot infect a new host cell.
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. -The phage lyses the bacterium and releases resistance genes into the local environment, which can then be taken up by recipient cells. -The phage causes the destruction of any antibiotic present during the specialized transduction process.
The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA.
How do restriction enzymes cut DNA sequences? -They cut DNA at sites, called recognition sites, that have specific nucleotide sequences. -They cut DNA at sequences that have lots of adenine bases. -They have the ability to cut DNA randomly.
They cut DNA at sites, called recognition sites, that have specific nucleotide sequences
How is a complex transposon different from a simple transposon? -They always integrate in multiple copies into the host genome. -Complex transposons code for different types of transposase. -They have two simple transposons with another DNA sequence between them. -Complex transposons have one very long insertion sequence.
They have two simple transposons with another DNA sequence between them.
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 -To replace a defective gene with a working gene -To remove an undesirable gene -To insert a desirable 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? -The bacteriophage does not erupt from an infected cell during transduction. -The bacteriophage takes fragments of the cell with it during transduction. -Transduction transfers DNA from the chromosome of one cell to another.
Transduction transfers DNA from the chromosome of one cell to another
Ionizing radiation does NOT include.. -gamma rays. -UV rays. -X-rays. -cosmic rays.
UV rays
Which of the following is NOT required for homologous recombination? -endonuclease -RecA -proteins having helicase activity -an Hfr chromosome
an Hfr chromosome
A deleterious mutation in recA results in -an increase in homologous recombination. -a decrease in specific recombination. -a decrease in homologous recombination. -no change in either general or specific recombination.
a decrease in homologous recombination.
A point mutation refers to mutations involving -the gain of a base pair (microinsertion). -a base-pair substitution. -the deletion of a base pair (microdeletion). -a substitution, deletion, or addition of one base-pair.
a substitution, deletion, or addition of one base-pair
A mutant that has a nutritional requirement for growth is an example of a(n) -auxotroph. -autotroph. -organotroph. -heterotroph.
auxotroph
A nucleotide-altering chemical -can alter nitrogenous bases of DNA, resulting in incorrect base pairing. -can cause double-stranded breaks in the DNA. -can be incorporated into the DNA, to cause a mispairing of bases. -can slip in between stacked bases, causing bulges in the DNA structure.
can alter nitrogenous bases of DNA, resulting in incorrect base pairing
The enzyme transposase may be coded for by insertion sequences on a.. -plasmid. -phage. -chromosome. -chromosome, phage, or plasmid.
chromosome, phage, or plasmid
The production of a functional gene product by transforming bacteria that lack a lacZ gene with a plasmid containing a lacZ gene is known as -complementation. -reversion. -transfection. -mitosis.
complementation
Plasmids that govern their own transfer are known as.. -transfective. -transformable. -transmutable. -conjugative.
conjugative
A transducing phage -cannot infect new host cells. -contains fragments of the host chromosome instead of the viral genome. -is a lysogenic bacteriophage. -has a viral coat made of host proteins.
contains fragments of the host chromosome instead of the viral genome
When damaged or single-stranded DNA activates the RecA protein, the RecA protein stimulates the cleavage of LexA. This results in... -increased transduction and recombination. -repression of polymerase V and activation of endonuclease. -derepression of the SOS system. -activation of the Hfr system.
derepression of the SOS system
F- strains of Escherichia coli -do not have an F factor. -have the F factor as a plasmid. -have an integrated F factor. -transfer the F factor to other strains at a high frequency.
do NOT have an F factor.
The killing of cells by UV irradiation involves -formation of purine dimers. -absorption at 260 nm by proteins only. -absorption at 260 nm by RNA only. -formation of pyrimidine dimers.
formation of pyrimidine dimers
Microinsertions and microdeletions often result in ________ mutations. -frameshift -silent -advantageous -auxotrophic
frameshift
Genetic recombination involving insertion sequences typically results in what type of mutation? -frameshift mutation -base-pair deletion mutation -base-pair substitution mutation -silent mutation
frameshift mutation
Which process listed below allows genetic material to be transferred from a virus-like particle that lacks genes for its own replication? -transformation of a linear piece of DNA -gene transfer through a gene transfer agent -conjugation of an F+ plasmid -transduction by a dsDNA phage Mu
gene transfer through a gene transfer agent
Hfr strains of Escherichia coli -do not possess an F factor. -have an integrated F factor. -have the F factor as a plasmid. -transfer the complete F factor to recipient cells at a high frequency.
have an integrated F factor
F+ strains of Escherichia coli -have an integrated F factor. -have the F factor as a plasmid. -do not have an F factor. -transfer the F factor to recipient cells at a high frequency.
have the F factor as a plasmid
The process in which related DNA sequences from two different sources are exchanged is called -transduction. -homologous recombination. -reversion. -phage conversion.
homologous recombination
Mutagens -are the sole cause of mutations in DNA. -decrease the likelihood of mutations in DNA. -increase the likelihood of mutations in DNA. -come in two basic forms: ionizing and nonionizing radiation.
increase the likelihood of mutations in DNA
Chemical mutagens, UV radiation, and ionizing radiation all increase mutation rates, but they have different mechanisms. Which type of mutagen would be best suited for creating large deletions and rearrangements within a genome? -UV radiation -chemical mutagens -ionizing radiation -Chemical, UV, and ionizing radiation would create large deletions and rearrangements if used in a very high dose.
ionizing radiation
Transversion is a mutation that -DNA fragment is moved to another location -is a point mutation where purines are replaced by pyrimidines or vice versa -it is not a mutation -purines are substituted by other purines
is a point mutation where purines are replaced by pyrimidines or vice versa
Integration of linear transforming DNA into the chromosome... -is catalyzed by the RecA gene. -is not required for the expression for the transformed genes. -almost never occurs because restriction endonuclease will degrade the DNA before it is integrated. -only occurs in laboratory-based systems in artificial competent cells.
is catalyzed by the RecA gene.
If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium without ampicillin, it may -transfer resistance to other cultures in the laboratory. -undergo a reversion mutation. -gain resistance to other antibiotics. -lose the plasmid because there is no selection for ampicillin resistance.
lose the plasmid because there is no selection for ampicillin resistance
Selectable mutation is.. -mutation that confers advantage -a mutation that chnages only one base pair -opccurs without external intervention -a mutation selected in the lab
mutation that confers advantage
Thymine dimers result from -nonionizing radiation. -ionizing radiation. -mistakes by DNA polymerase. -nucleoside analogs.
nonionizing radiation
The mutagens 2-aminopurine and 5-bromouracil are examples of.. -nucleotide base analogs. -alkylating agents. -chemicals reacting with DNA. -None of the answers are correct.
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. -transduction -SOS repair -pili -transformation
pili
A mutation that readily reverses to restore the original parental type would most likely be due to a(n) -deletion. -frameshift mutation. -insertion. -point mutation.
point mutation
A plasmid may -replicate independently of the chromosome. -be integrated into the chromosome. -replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation. -be transferred cell-to-cell during conjugation.
replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation
High-efficiency, natural transformation -is only common in Archaea. -is common in Bacteria and Archaea. -requires specialized DNA uptake, DNA binding, and integration proteins. -usually involves plasmids.
requires specialized DNA uptake, DNA binding, and integration proteins
All Hfr strains integrate into the chromosome at -several specific sites. -the same locus. -the same locus most of the time, although there may be some variation. -loci that cannot be accurately determined.
several specific sites
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 -nonsense mutation -missense mutation -frameshift mutation
silent mutation
Transposition is a(n) -homologous recombination event. -general recombination event. -analogous recombination event. -site-specific recombination event.
site-specific recombination event
When a transducing phage interacts with a new host cell, -the DNA from the previous host can recombine with the new host chromosome. -it will cause the new cell to produce more transducing phage. -the new host cell will be lysed.
the DNA from the previous host can recombine with the new host chromosome
What makes an insertion sequence different from other DNA sequences found in a cell? -They can integrate into the cell genome. -They contain inverted repeats. -They are capable of effecting their own movement from one location to another on DNA.
they are capable of effecting their own movement from one location to another on DNA.
The uptake of free DNA from the environment ________, while transfer of DNA with cell-to-cell contact would most likely result in ________. -transformation / conjugation -transformation / transduction -transduction / conjugation -conjugation / transformation
transformation / conjugation
Which of the following methods may introduce foreign DNA into a recipient? -conjugation -transformation -transduction -transformation, transduction, and conjugation
transformation, transduction, and conjugation
The SOS system repairs DNA that has gaps, breaks, and other lesions by -using available mRNA and a special RNA-dependent DNA polymerase to fill in the gaps and replace damaged DNA. -cutting DNA from other parts of the genome and pasting it into the gaps or damaged areas. -using specialized DNA polymerases that will synthesize a new DNA strand even if there is not a normal complementary DNA strand to act as a template. -stabilizing single-stranded DNA until the next round of normal replication.
using specialized DNA polymerases that will synthesize a new DNA strand even if there is not a normal complementary DNA strand to act as a template.