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Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Describe the state of the F factor.Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Which of these cells are donors? Which is the recipient?Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Which of these donors can convert exconjugants to a donor state?Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Which of these donors can transfer a donor gene to exconjugants?Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Describe the results of conjugation (i.e., changes in the recipient and the exconjugant) that allow detection of the state of the F factor in a donor strain.Problem 1
For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following. Describe a 'partial diploid' and how it originates.Problem 2
The flow diagram identifies relationships between bacterial strains in various F factor states. For each of the four arrows in the diagram, provide a description of the events involved in the transition.Problem 3
Conjugation between an Hfr cell and an F⁻ cell does not usually result in conversion of exconjugants to the donor state. Occasionally, however, the result of this conjugation is two Hfr cells. Explain how this occurs.Problem 4
Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.
Using terminology from the chapter, characterize the 12 colonies that grow on minimal medium and the 3 colonies that do not.Problem 4
Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.
The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine and all three colonies grow. Characterize these three colonies.Problem 4
Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.
The serine biosynthetic pathway is a three-step pathway in which each step is catalyzed by the enzyme product of a different gene, identified as enzymes A, B, and C in the diagram below.
Mutant 1 grows only on In addition to growth on , mutant 2 also grows on and . Mutant 3 grows on and . Identify the step of the serine biosynthesis pathway at which each mutant is defective.
Problem 4
Bacteria transfer genes by conjugation, transduction, and transformation. Compare and contrast these mechanisms. In your answer, identify which if any processes involve homologous recombination and which if any do not.Problem 5
Explain the importance of the following features in conjugating donor bacteria:
the conjugation pilusProblem 5
Explain the importance of the following features in conjugating donor bacteria:
homologous recombinationProblem 5
Explain the importance of the following features in conjugating donor bacteria:
the relaxosomeProblem 5
Explain the importance of the following features in conjugating donor bacteria:
relaxaseProblem 5
Explain the importance of the following features in conjugating donor bacteria:
T strand DNAProblem 5
Explain the importance of the following features in conjugating donor bacteria: the origin of transferProblem 5
Explain the importance of the following features in conjugating donor bacteria:
pilin proteinProblem 7
Describe what is meant by the term site-specific recombination as used in identifying the processes that lead to the integration of temperate bacteriophages into host bacterial chromosomes during lysogeny or to the formation of specialized transducing phage.
Problem 8
What is a prophage, and how is a prophage formed?
Problem 9
How is the frequency of cotransduction related to the relative positions of genes on a bacterial chromosome? Draw a map of three genes and describe the expected relationship of cotransduction frequencies to the map.Problem 10
Describe the differences between genetic complementation and recombination as they relate to the detection of wild-type lysis by a mutant bacteriophage.
Problem 11
Among the mechanisms of gene transfer in bacteria, which one is capable of transferring the largest chromosome segment from donor to recipient? Which process generally transfers the smallest donor segments to the recipient? Explain your reasoning for both answers.
Problem 12
What is lateral gene transfer? How might it take place between two bacterial cells?
Problem 13
Lateral gene transfer is thought to have played a major role in the evolution of bacterial genomes. Describe the impact of LGT on bacterial genome evolution.
Problem 14
Seven deletion mutations (1 to 7 in the table below) are tested for their ability to form wild-type recombinants with five point mutations (a to e). The symbol "+" indicates that wild-type recombination occurs, and "-" indicates that wild types are not formed. Use the data to construct a genetic map of the order of point mutations, and indicate the segment deleted by each deletion mutation.
Problem 15
A 2013 CDC report identified the practice of routinely adding antibiotic compounds to animal feed as a major culprit in the rapid increase in the number of antibiotic-resistant strains. Agricultural practice in recent decades has encouraged the addition of antibiotics to animal feed to promote growth rather than to treat disease.
Speculate about the process by which feeding antibiotics to animals such as cattle might lead to an increase in the number of antibiotic-resistant strains of bacteria.Problem 15
A 2013 CDC report identified the practice of routinely adding antibiotic compounds to animal feed as a major culprit in the rapid increase in the number of antibiotic-resistant strains. Agricultural practice in recent decades has encouraged the addition of antibiotics to animal feed to promote growth rather than to treat disease.
How might the increase in antibiotic-resistant strains of bacteria in cattle be a threat to human health?Problem 16
Hfr strains that differ in integrated F factor orientation and site of integration are used to construct consolidated bacterial chromosome maps. The data below show the order of gene transfer for five strains.
Hfr Strain Order of Gene Transfer (First → Last)
Hfr A oriT–thr–leu–azi–ton–pro–lac–ade
Hfr B oriT–mtl–xyl–mal–str–his
Hfr C oriT–ile–met–thi–thr–leu–azi–ton
Hfr D oriT–his–trp–gal–ade–lac–pro–ton
Hfr E oriT–thi–met–ile–mtl–xyl–mal–str
Identify the overlaps between Hfr strains. Identify the orientations of integrated F factors relative to one another.
