Exam 3: possible questions Flashcards
Phage antiholins form holes in the membrane and holins prevent them.
FALSE.
Filamentous phages (M13 and f1) leak out of the cells using a modified type II secretion system.
TRUE.
Site-directed mutagenesis of Rv2275 and cyp121 genes was done in the In-Fusion kit.
FALSE.
The uptake of bacterial virus DNA is released is ______, while the transfer of bacterial DNA with cell-to-cell contact would most likely result in _____.
transfection/conjugation.
Which of the following is NOT a characteristic of the F plasmid?
Uses semiconservative replication involving the host’s machinery.
Most phages cause acute infections and lyse their host.
TRUE.
Which of the following is NOT a potential fate of foreign DNA transferred via conjugation?
- degradation by restriction enzymes
- recombination with the host chromosome
- replication by itself (if containing an origin f replication)
- ALL OF THE ABOVE ARE POTENTIAL FATES (answer)
Lytic phages are commonly used as antimicrobials to kill antibiotic-resistant bacteria.
FALSE.
Which of the following statements is true about the role of the Dpnl enzyme in the site-directed mutagenesis kit you used?
To digest the parental template DNA after amplification step.
(not sure)
The frequency of transfer of an F’ molecule by conjugation is closest to the frequency of transfer of:
an F plasmid by conjugation.
check slide 1 on ch.5
Which of the following statements is false about the true restriction-modification systems?
Consists of endonucleases capable to cut single-stranded DNA at specific DNA sequences.
Which of the following statements is FALSE about the relaxase enzyme?
Is involved in DNA replication.
Some lysis proteins activate enzymes that make precursors of the bacterial cell walls by binding to them.
FALSE.
check answer
F+ strains of Escherichia coli:
have the F factor as a plasmid.
Which of the following statements is/are true?
(its ALL OF THE ABOVE)
-In Abi (abortive infection) system, phage infection starts normally and suddenly stops
because the host cell dies.
-Abi is comparable to apoptosis in multicellular eukaryotes.
-Mechanisms that induce cell death include destruction of membrane potential and
blockage of cellular translation.
Which of the following statements is FALSE about T4 gene expression?
Delayed-early genes are transcribed from s70 promoters but requires antitermination factors encode by true-late genes.
(Ch. 7 slide 12)
You transformed E. coli with different ligation reaction combinations and after O/N incubators you get:
- No DNA control: 100 colonies
- cloning vector alone: 250 colonies
- Cloning vector plus insert: 300 colonies.
- What is the next course of action?
-Start over the transformation with a new batch of LB agar plates containing the appropriate selection antibiotic.
-Redo the cloning reaction with the insert with better preparation of the cloning vector and retransform.
(both answers)
Which of the following statements is/are FALSE about transformation?
Only gram+ bacteria can exchange DNA by transformation.
Which of the following statements is/are TRUE about natural transformation?
(both are true)
- Is a process that could be regulated by quorum sensing.
- DNA enters the cells by an active transport mechanism.
An F pilus is essentail for:
- DNA-mediated transformation
- chromosome transfer by conjugation
- plasmid transfer by conjugation
- recombination
- cell movement
answer: 2 and 3.
Transformation of Mycobacterium smegmatis is done by using chemically-competent cells.
FALSE.
When F+ donor gives an F plasmid to an F-recipient:
both become F+.
ch5 slide 1
Filamentous phages cause chronic infection as the host cells are killed.
FALSE.
ch7 slide 20
Which if the following is/are TRUE about the phage multiplication cycle?
Many phages inject their genome in the host bacteria.
Which of the following statements is/are true about the use of the T7 RNA polymerase gene in the protein expression system?
A copy of the T7 RNA polymerase gene under the control of an IPTG-inducible promoter is included in a DE3 lysogen.
Which of the following statements is false about CRISPR?
CRISPR is a defense mechanism targeting mRNA.
A mutation in most genes only affects the product of the gene, while a mutation in a regulatory gene can affect the expression of many genes.
TRUE.
Which of the following statements is FALSE?
The Rv2275-cyp121 operon was inserted into the pDTCF vector by ligation w/ T4 DNA ligase.
Which of the following is/are FALSE about phage gene expression?
All phages carry their own polymerase(s) in the capsid.
Which of the following statements is/are FALSE about the phage T4?
-T4 encodes its own enzymes for DNA replication.
(B and D are false) is answer choice on pdf.
The addition of DNase to a mixture of donor and recipient cells will prevent gene transfer via:
Transformation.
Which method(s) can be used to increase the concentration of DNA in the solution?
Precipitation in ethanol in the presence with sodium acetate.
Which of the following statements is/are TRUE about bacteriophages?
(both are TRUE)
- On Earth, there are more phages than bacteria.
- Phages form a relatively small number of families, with very little relationship between families.
Which of the following statements is/are FALSE about T4 gene expression?
The expression of early genes is coupled to the T4 DNA replication.
(False because transcription of true late genes coupled to phage DNA replication)
A bacterial cell that is able to take up naked DNA is said to be:
Competent.
