Question 1

In a conjugation experiment not all of the cells receiving two genes will demonstrate an altered phenotype for both genes. What is the most likely explanation of this phenomenon?
A) One gene is toxic to the cell
B) Transferred genes must undergo recombination for genotypic conversion of the recipient cell and there is a possibility that only one gene will be recombined into the recipients chromosome
C) The transferred DNA is rapidly degraded by the recipient cell and one gene can be degraded before it is recombined into the host chromosome
D) It is not physically possible to recombine more than one gene into a single host genome per conjugation event

Accepted Answer

In conjugation, the transferred genes must undergo recombination for genotypic conversion of the recipient cell, and there is a possibility that only one gene will be recombined into the recipient's chromosome, leading to the unaltered phenotype for the other gene.

Question 2

An Hfr strain is produced when
A) an F episome integrates into the E. coli chormosome.
B) an F episome leaves the E. coli chromosome.
C) an F episome is transferred to a new cell.
D) an F episome leaves the host chromosome and removes some of the host chromosome.

Accepted Answer

An Hfr (High frequency of recombination) strain is produced when the F episome integrates into the E. coli chromosome, resulting in the transfer of part of the host chromosome along with the episome during conjugation. This integration makes the transfer of the entire episome less efficient and increases the frequency of recombination between the donor and recipient cells.

Question 3

In the experiment performed by Benzer for intragenic mapping which of the following is the most critical control?
A) Perform the experiment with each different virus alone to determine the rate of reversion mutation
B) Re-type the strain of E. coli
C) Test the agar to make sure it can support E. coli and viral growth
D) Perform at least five dilutions to make sure the dilutions were performed correctly

Accepted Answer

The most critical control in this experiment would be to determine the rate of reversion mutation for each different virus alone. This is important because the experiment relies on the assumption that the spontaneous mutations are random and occur at a constant rate. By measuring the rate of reversion mutation for each virus alone, Benzer can ensure that any differences he observes in the intragenic mapping experiment are actually due to differences in the genetic material and not due to different rates of mutation.

Question 4

What is the correct order for the steps in transduction?
A) 1) Phage infects cell 2) Phage transported DNA recombines with chromosome of new cell 3) Host DNA digested into fragments 4) Some phage accidently carry host DNA fragment 5) Phage infects new cell
B) 1) Phage infects cell 2) Phage transported DNA recombines with chromosome of new cell 3) Host DNA digested into fragments 4) Phage infects new cell 5) Some phage accidently carry host DNA fragment
C) 1) Phage infects cell 2) Host DNA digested into fragments 3) Some phage accidently carry host DNA fragment 4) Phage infects new cell 5) Phage transported DNA recombines with chromosome of new cell
D) 1) Phage infects cell 2) Phage transported DNA recombines with chromosome of new cell 3) Some phage accidently carry host DNA fragment 4) Phage infects new cell 5) Host DNA digested into fragments

Accepted Answer

The correct order of steps in transduction is: 1) Phage infects cell, 2) Host DNA is digested into fragments, 3) Some phages accidentally carry host DNA fragments, 4) Phage infects a new cell, 5) Phage-transported DNA recombines with the chromosome of the new cell.

Question 5

Complementation experiments are used to determine if two observed mutations that are associated with the same trait are actually in the same gene.

Accepted Answer

Complementation experiments involve crossing two individuals with different mutations and observing the offspring. If the mutations are in different genes, the offspring will show the phenotype associated with both mutations. However, if the mutations are in the same gene, the offspring will show a phenotype that is similar to only one of the mutations. Therefore, complementation experiments can be used to determine if two observed mutations that are associated with the same trait are actually in the same gene.

Question 6

In the Lederberg and Tatum experiment what is the purpose of performing the experiment with the strains without adding them together?
A) It serves as a control to calculate the rate of reversion mutations
B) There is no experimental purpose to performing that part of the experiment
C) It tests that the strains were made correctly
D) It tests to make sure the media was made correctly

Accepted Answer

Performing the experiment with the strains without adding them together serves as a control to calculate the rate of reversion mutations. This allows for a comparison of the mutation rate between the two strains when they are combined, and helps to determine if the observed genetic changes were a result of the combination of the two strains or simply a spontaneous mutation.

Question 7

Most biologists consider viruses to be living organisms, which are classified with the bacteria.

Accepted Answer

Most biologists consider viruses to be non-living entities, as they lack the ability to reproduce and carry out metabolic processes on their own. They are classified separately from bacteria as they have distinct differences in structure, composition, and behavior.

Question 8

Although there are several different types of plasmids they all
A) can confer some kind of selective growth advantage depending on environmental conditions.
B) can induce a mating phenotype.
C) result in horizontal transfer.
D) make cells resistant to antibiotics

Accepted Answer

Plasmids can confer a variety of selective growth advantages to bacteria depending on the environmental conditions, such as antibiotic resistance, metal resistance, or the ability to metabolize unusual substances, enhancing the survival and adaptability of the host cell in different environments.

Question 9

In an experiment with an Hfr cell if the uvrA gene is transferred 1 minute and the pyrB gene is transferred at 2.5 minutes then where is the oriT of the Hfr cell located? Use the map of the
A) 70 minutes
B) 90 minutes
C) 100 mintues
D) 97.5 minutes

Accepted Answer

The answer of In an experiment with an Hfr cell...

Question 10

Acquired antibiotic resistance between two different species is an example of vertical gene transfer.

Accepted Answer

Vertical gene transfer refers to the transfer of genetic material from one generation to the next. Acquired antibiotic resistance between two different species occurs through horizontal gene transfer, which is the transfer of genetic material between different organisms that are not related through sexual reproduction.

Question 11

What strategy did Benzer use to perform intragenic mapping?
A) Infection of a cell with two different viruses that had mutations in the same gene could not result in a wild type virus by recombination
B) Infection of a cell with two different viruses that had mutations in the same gene would result in a wild type virus by transduction
C) Infection of a cell with two different viruses that had mutations in different genes could result in a wild type virus by recombination
D) Infection of a cell with two different viruses that had mutations in the same gene could result in a wild type virus by recombination

Accepted Answer

Benzer used the strategy of infecting a cell with two different viruses that had mutations in the same gene. This allowed for the possibility of recombination between the two viruses, resulting in a wild type virus. The frequency of recombination allowed Benzer to map the location of the mutations within the gene.

Question 12

Which statement is true concerning intragenic and intergenic gene mapping?
A) The number of expected wild type recombinant viruses will be greater in intragenic mapping than with intergenic mapping
B) Intergenic gene mapping can only be performed in viruses.It is not performed in bacteria while intragenic mapping is performed in both viruses and bacteria
C) Intragenic mapping is the mapping of mutations within a gene while intergenic mapping is the mapping of genes with respect to each other
D) Intergenic mapping is the mapping of mutations within a gene while intragenic mapping is the mapping of genes with respect to each other

Accepted Answer

Intragenic mapping is focused on identifying mutations within a single gene, while intergenic mapping is focused on determining the location and arrangement of genes relative to each other. Choice A is incorrect because the number of wild type recombinants is typically greater in intergenic mapping. Choice B is incorrect because both intragenic and intergenic mapping can be performed in both viruses and bacteria. Choice D is incorrect because it swaps the definitions of intragenic and intergenic mapping.

Question 13

The transfer of genetic material from two unrelated species is called ________.
A) Vertical gene transfer
B) Conjugation
C) Sexual reproduction
D) Binary fission
E) Horizontal gene transfer

Accepted Answer

Horizontal gene transfer is the transfer of genetic material (such as plasmids or transposons) between two unrelated organisms, which may occur through a variety of mechanisms including transformation, transduction, and conjugation. Vertical gene transfer, on the other hand, is the transfer of genetic material from parent to offspring through reproduction (such as sexual or asexual reproduction). Conjugation is a specific type of horizontal gene transfer that involves the direct transfer of DNA between two bacterial cells through a conjugation bridge. Sexual reproduction and binary fission are not related to gene transfer between different species.

Question 14

Competent cells are those used in studies of conjugation.

Accepted Answer

Competent cells are specially treated bacterial cells that are capable of taking up foreign DNA from their environment, a process used in molecular cloning, not specifically for studies of conjugation. Conjugation involves direct transfer of DNA between two bacterial cells.

Question 15

In formation of plaques by bacteriophages which of the following statements is true?
A) A plaque is the result of several different viruses initially infecting a single cell
B) The plaque is the result of a single virus that has replicated in many bacterial cells in a localized area
C) A plaque results when a single virus infects one cell and then does not infect any other cell
D) Plaques are the areas where cells have not been infected at all

Accepted Answer

A plaque is formed when a single virus infects one bacterial cell and replicates within it, leading to the destruction of the cell and the release of new viruses. These new viruses then infect neighboring bacterial cells, leading to the formation of a localized area of bacterial cell death, which is referred to as a plaque. Plaques are often used as a measure of the viral infectivity or titer in a given sample.

Question 16

In the experiment performed by Lederberg and Tatum bacteria of different genotypes had to be mixed together to obtain genetic transfer. However, Davis performed the experiment in a slightly different manner by separating cells with a filter incapable of allowing bacteria to pass. What possibility did the experiment by Davis exclude that could have occurred by the protocol used by Lederberg and Tatum?
A) transformation
B) conjugation
C) generalized transduction
D) specialized transduction

Accepted Answer

The answer of In the experiment performed by Lederberg and...

Question 17

The results below are from an interrupted conjugation experiment performed with an Hfr strain. Which genes could also be mapped with generalized transduction? 
A) argR and argG only
B) All three could be mapped to each other using generalized transduction
C) argR could be mapped to recA and argG could be mapped to recA but argR and argG are too close to each other to be mapped using generalized transduction
D) Only argG could be mapped with recA since argR is farther away from recA there would be little recombination that would include all three genes together and so argR could not be reliably mapped using generalized transduction.

Accepted Answer

The answer of The results below are from an interrupted...

Question 18

An episome is a segment of bacterial DNA that can exist as a plasmid or be integrated into the bacterial chromosome.

Accepted Answer

An episome is indeed a segment of bacterial DNA that can exist as a plasmid or be integrated into the bacterial chromosome.

Question 19

How can the complementation test discriminate between two viruses that have a mutation in the same gene versus two viruses that have mutations in the same gene?
A) If the viruses have mutations in the same gene then, depending on the assay, a significant number of plaques will be produced or a significant number of plaques will have a wildtype phenotype. If the mutations are in the different genes few, if any, wild type plaques will be seen..
B) If the viruses have mutations in different genes then, depending on the assay, a significant number of plaques will be produced or a significant number of plaques will have a wildtype phenotype. If the mutations are in the same gene few, if any, wild type plaques will be seen.
C) If the mutations are in the same gene the complementation test will result in recombinant viruses that are wildtype but if the mutations are in different genes no recombinant viruses will be produced.
D) If the mutations are in different genes the complementation test will result in recombinant viruses that are wildtype but if the mutations are in the same gene no recombinant viruses will be produced.

Accepted Answer

The complementation test involves co-infecting cells with two viruses, each with a mutation in the same gene, to determine whether or not the mutations are in the same or different genes. If the mutations are in different genes, the viruses can complement each other and produce a wildtype phenotype, resulting in a significant number of plaques with a wildtype phenotype. If the mutations are in the same gene, the viruses will not complement each other and no wildtype plaques will be seen. Therefore, B is the correct answer.

Quiz 7: Genetic Transfer and Mapping in Bacteria and Bacteriophages

In a conjugation experiment not all of the cells receiving two genes will demonstrate an altered phenotype for both genes. What is the most likely explanation of this phenomenon?

An Hfr strain is produced when

In the experiment performed by Benzer for intragenic mapping which of the following is the most critical control?

What is the correct order for the steps in transduction?

Complementation experiments are used to determine if two observed mutations that are associated with the same trait are actually in the same gene.

In the Lederberg and Tatum experiment what is the purpose of performing the experiment with the strains without adding them together?

Most biologists consider viruses to be living organisms, which are classified with the bacteria.

Although there are several different types of plasmids they all

In an experiment with an Hfr cell if the uvrA gene is transferred 1 minute and the pyrB gene is transferred at 2.5 minutes then where is the oriT of the Hfr cell located? Use the map of the

Acquired antibiotic resistance between two different species is an example of vertical gene transfer.

What strategy did Benzer use to perform intragenic mapping?

Which statement is true concerning intragenic and intergenic gene mapping?

The transfer of genetic material from two unrelated species is called ________.

Competent cells are those used in studies of conjugation.

In formation of plaques by bacteriophages which of the following statements is true?

The results below are from an interrupted conjugation experiment performed with an Hfr strain. Which genes could also be mapped with generalized transduction?

An episome is a segment of bacterial DNA that can exist as a plasmid or be integrated into the bacterial chromosome.

How can the complementation test discriminate between two viruses that have a mutation in the same gene versus two viruses that have mutations in the same gene?