Faulty outlooping produces A phage containing bacterial DNA (a) Production of lysogen Attachment sites gal bio gal bio (b) Production of initial lysate gal (0 Normal outlooping bio bio Mixture Adgal gal gal bio bio () Rare abnormal outlooping (c) Transduction by initial lysate Adgal A helper bio () Lysogenic transductants bio (1) Transductants produced by recombination gal gal bio FIGURE 5-33 The diagram shows how specialized transduction operates in phage a) A crossover at the specialzed attachment site produces a lysogenic bacterium. (b) The ysogenic bacterium can produce a nomal A or, rarely, Adgal , a transducing particle containing the gal gene. (c) gal" transductants can be produced by either ) the co- ncorporation of Xdgal and X (acting as a helper) or () crossovers fanking the gal gene, a are event. The blue double boxes are the bacterial attachment site, the purple double poxes are the A attachment site, and the pairs of blue and purple baxes are hybrid ntegration sites, derived partly from E coli and partly from .

Faulty outlooping produces A phage containing bacterial DNA (a) Production of lysogen Attachment sites gal bio gal bio (b) Production of initial lysate gal (0 Normal outlooping bio bio Mixture Adgal gal gal bio bio () Rare abnormal outlooping (c) Transduction by initial lysate Adgal A helper bio () Lysogenic transductants bio (1) Transductants produced by recombination gal gal bio FIGURE 5-33 The diagram shows how specialized transduction operates in phage a) A crossover at the specialzed attachment site produces a lysogenic bacterium. (b) The ysogenic bacterium can produce a nomal A or, rarely, Adgal , a transducing particle containing the gal gene. (c) gal" transductants can be produced by either ) the co- ncorporation of Xdgal and X (acting as a helper) or () crossovers fanking the gal gene, a are event. The blue double boxes are the bacterial attachment site, the purple double poxes are the A attachment site, and the pairs of blue and purple baxes are hybrid ntegration sites, derived partly from E coli and partly from .

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter8: The Structure, Replication, And Chromosomal Organization Of Dna

Section: Chapter Questions

Problem 6QP: Recently, scientists discovered that a rare disorder called polkadotism is caused by a bacterial...

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An ade+ arg+ cys+ his+ leu+ pro+ bacterial strain is knownto be lysogenic for a newly discovered phage, but the siteof the prophage is not known. The bacterial map isleucysarghisadeproThe lysogenic strain is used as a source of the phage, andthe phages are added to a bacterial strain of genotypeade- arg- cys- his- leu- pro-. After a short incubation,samples of these bacteria are plated on six differentmedia, with the supplementations indicated in thefollowing table. The table also shows whether colonieswere observed on the various media.PresenceMedium Ade Arg Cys His Leu Pro of colonies1 - + + + + + N2 + - + + + + N3 + + - + + + C4 + + + - + + N5 + + + + - + C6 + + + + + - NNutrient supplementation in medium(In this table, a plus sign indicates the presence of anutrient supplement, a minus sign indicates that asupplement is not present, N indicates no colonies, and Cindicates colonies present.)a. What genetic process is at work here?b. What is the approximate locus of the prophage?
As described in Figure, host DNA is hydrolyzed into smallpieces, which are occasionally assembled with phage proteins, creatinga phage with bacterial chromosomal DNA. If the breakage ofthe chromosomal DNA is not random (i.e., it is more likely tobreak at certain spots as opposed to other spots), how might nonrandombreakage affect cotransduction frequency?
In the lysogenic cycle of bacteriophages, which of the fol-lowing is true?(a) Lysogeny is the term applied to a temperate phage thatdoes not replicate itself independently and does not lysethe bacterial host cell.(b) Phage DNA is incorporated into the host bacterium’sDNA, at which time it is called a prophage.(c) Temperate phages can be replicated either as a pro-phage along with bacterial chromosomal replicationor can suddenly revert to the lytic cycle by replicatingthemselves and assembling into new phages.(d) All the above are true.(e) a and c only.
Host DNA is digested into small pieces, which are occasionally assembled with phage proteins, creating a phage with bacterial chromosomal DNA. If the breakage of the chromosomal DNA is not random (i.e., it is more likely tobreak at certain spots as opposed to other spots), how might suchnonrandom breakage affect cotransduction frequency?
Genome sequences show that some pathogenic bacteriacontain virulence genes that promote disease next togenes that originally came from bacteriophage. Whydoes this result suggest horizontal gene transfer, andwhat would the mechanism of transfer have been?
The terms conjugation, transduction, and transformation are usedto describe three different natural forms of genetic transferbetween bacterial cells. Briefly discuss the similarities and differencesamong these processes?
In two isolates (one is resistant to ampicillin and theother is sensitive to ampicillin) of a new bacterium,you found that genes encoding ampicillin resistanceare being transferred into the sensitive strain. . To determine if the gene transfer involves transformation, conjugation, or transduction, you separatethe ampicillin-resistant and ampicillin-sensitivestrains by a membrane with pores that are smallerthan the size of a bacterium, but larger than thesizes of bacteriophage or DNA fragments. If genetransfer is still observed, what mechanisms arepossibly involved and which are excluded?
A researcher identified a mutation in PR of phage λ that causes itstranscription rate to be increased 10-fold. Do you think this mutationwould favor the lytic or lysogenic cycle? Explain your answer.
By conducting conjugation experiments between Hfr and recipientstrains, Wollman and Jacob mapped the order of many bacterialgenes. Throughout the course of their studies, they identified severaldifferent Hfr strains in which the F-factor DNA had been integratedat different places along the bacterial chromosome. A sample oftheir experimental results is shown in the following table: A. E xplain how these results are consistent with the idea that thebacterial chromosome is circular.B. Draw a map of the bacterial chromosome that shows the orderof genes and the locations of the origins of transfer among thesedifferent Hfr strains.
Let’s suppose a new strain of P1 phage has been identified thatpackages larger pieces of the E. coli chromosome. This P1 strainpackages pieces of the E. coli chromosome that are 5 minuteslong. If two genes are 0.7 minute apart along the E. coli chromosome,what would be the cotransduction frequency using a normalstrain of P1 and using the new strain of P1 that packages largerpieces? What would be the experimental advantage of using thisnew P1 strain?
Generalized and specialized transduction both involvebacteriophages. What are the differences betweenthese two types of transduction?
In a genetics lab, Kim and Maria infected a samplefrom an E. coli culture with a particular virulent bacteriophage. They noticed that most of the cells werelysed, but a few survived. The survival rate in theirsample was about 1 × 10−4. Kim was sure the bacteriophage induced the resistance in the cells, whileMaria thought that resistant mutants probably alreadyexisted in the sample of cells they used. Earlier, for adifferent experiment, they had spread a dilute suspension of E. coli onto solid medium in a large petri dish,and, after seeing that about 105colonies were growingup, they had replica-plated that plate onto three otherplates. Kim and Maria decide to use these plates totest their theories. They pipette a suspension of thebacteriophage onto each of the three replica plates.What should they see if Kim is right? What shouldthey see if Maria is right?