C11 Sample Questions from Brock Flashcards
A mutant that has a nutritional requirement for growth is an example of a(n)
A) autotroph.
B) auxotroph.
C) heterotroph.
D) organotroph.
B) auxotroph.
An auxotroph requires a specific nutrient for growth due to a mutation.
Which of the following methods may introduce foreign DNA into a recipient?
A) transformation
B) transduction
C) conjugation
D) transformation, transduction, and conjugation
D) transformation, transduction, and conjugation
All three are mechanisms of horizontal gene transfer.
Consider the following experiment. First, large populations of two mutant strains of Escherichia coli are mixed, each requiring a different, single amino acid. After plating them onto a minimal medium, 45 colonies grew. Which of the following may explain this result?
A) The colonies may be due to back mutation (reversion).
B) The colonies may be due to recombination.
C) Either A or B is possible.
D) Neither A nor B is possible.
C) Either A or B is possible.
Prototrophic colonies could arise from either reversion mutations restoring the ability to synthesize the required amino acid or recombination between the two mutants, creating a prototroph.
Lysogeny probably carries a strong selective advantage for the host cell because it
A) prevents cell lysis.
B) confers resistance to infection by viruses of the same type.
C) confers resistance to infection by viruses of a different type (or strain).
D) confers resistance to infection by many virus types and prevent cell lysis.
D) confers resistance to infection by many virus types and prevent cell lysis.
Lysogeny offers immunity to superinfection by similar phages and prevents lysis by integrating the phage genome into the host chromosome.
A plasmid may
A) replicate independently of the chromosome.
B) be transferred cell-to-cell during conjugation.
C) be integrated into the chromosome.
D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.
D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.
Plasmids can exist and be transferred in various ways.
Homologous recombination has been observed in
A) Archaea.
B) Bacteria.
C) Eukarya.
D) All three domains (Archaea, Bacteria, and Eukarya).
D) All three domains (Archaea, Bacteria, and Eukarya).
Homologous recombination is a fundamental process in all three domains of life.
Transposition is a(n)
A) homologous recombination event.
B) analogous recombination event.
C) site-specific recombination event.
D) general recombination event.
C) site-specific recombination event.
Transposition occurs at specific target sites in the DNA.
A ʺpoint mutation” refers to mutations involving
A) a base-pair substitution.
B) the gain of a base pair (microinsertion).
C) the deletion of a base pair (microdeletion).
D) a substitution, deletion, or addition of one base-pair.
D) a substitution, deletion, or addition of one base-pair.
Point mutations encompass single base-pair changes.
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
A) 1, 2, 3
B) 1, 2
C) 3, 4
D) 1, 2, 4
B) 1, 2
All three processes involve unidirectional gene transfer and may result in incomplete transfer. Homologous recombination is necessary for integration of the transferred DNA, but not an inherent part of the transfer process itself. Meiosis is not involved in bacterial gene transfer.
Which of the following factors has delayed the development of laboratory-based genetic systems in Archaea?
A) There are no documented systems of conjugation in Archaea.
B) Homologous recombination does NOT occur in Archaea.
C) Archaea do NOT host viruses or plasmids.
D) Many archaea grow in extreme or unusual conditions that make the use of agar and traditional mutant screening techniques problematic.
D) Many archaea grow in extreme or unusual conditions that make the use of agar and traditional mutant screening techniques problematic.
The extreme growth conditions of many archaea pose challenges for standard lab techniques.
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?
A) Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival.
B) Microorganisms carefully control the mutation rate of their DNA to match the environmental conditions and maximize evolution.
C) 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.
D) Constant mutation rates would halt evolution completely.
A) Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival.
Elevated mutation rates under stress can generate diversity that might include beneficial adaptations.
When DNA is transferred into a prokaryotic cell it may
A) be degraded by enzymes.
B) replicate independent of the host chromosome.
C) recombine with the host chromosome.
D) be degraded by enzymes, replicate independent of the host chromosome, or recombine with the host chromosome.
D) be degraded by enzymes, replicate independent of the host chromosome, or recombine with the host chromosome.
These are the possible fates of foreign DNA in a prokaryotic cell.
The process in which related DNA sequences from two different sources are exchanged is called
A) transduction.
B) phage conversion.
C) reversion.
D) homologous recombination.
D) homologous recombination.
Homologous recombination involves the exchange of similar DNA sequences.
High-efficiency, natural transformation
A) is common in Bacteria and
B) requires specialized DNA uptake, DNA binding, and integration proteins.
C) is only common in Archaea.
D) usually involves plasmids.
B) requires specialized DNA uptake, DNA binding, and integration proteins.
Natural transformation systems involve complex machinery for DNA uptake and processing.
The CRISPR system
A) facilitates homologous recombination through a complex system of proteins and clustered repeats.
B) recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.
C) repairs DNA and increases DNA damage tolerance during times of stress.
D) synthesizes gene transfer agents during stationary phase.
B) recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them. CRISPR systems provide adaptive immunity by targeting and destroying foreign DNA based on prior exposure.
