Lytic cycle Lysogenic cycle Phage DNA Bacteriophage Bacterial chromosome New phages Phage injects its DNA into cytoplasm. On rare occasions, a prophage may be excised from host can bind to bacterial cells. chromosome. 88 Phage DNA directs the synthesis of Phage DNA many new Cell lyses and releases integrates into host Prophage DNA is copied when cells divide. phages. Host DNA is digested the new phages. chromosome. into fragments. Prophage Fragment of bacterial chromosome FIGURE 18.4 The lytic and lysogenic reproductive cycles of certain bacteriophages. Some bacteriophages, known as virulent phages, can only follow a lytic cycle. Other phages, called temperate phages, can follow either a lysogenic or lytic cycle. 0

Lytic cycle Lysogenic cycle Phage DNA Bacteriophage Bacterial chromosome New phages Phage injects its DNA into cytoplasm. On rare occasions, a prophage may be excised from host can bind to bacterial cells. chromosome. 88 Phage DNA directs the synthesis of Phage DNA many new Cell lyses and releases integrates into host Prophage DNA is copied when cells divide. phages. Host DNA is digested the new phages. chromosome. into fragments. Prophage Fragment of bacterial chromosome FIGURE 18.4 The lytic and lysogenic reproductive cycles of certain bacteriophages. Some bacteriophages, known as virulent phages, can only follow a lytic cycle. Other phages, called temperate phages, can follow either a lysogenic or lytic cycle. 0

Biology: The Unity and Diversity of Life (MindTap Course List)

15th Edition

ISBN:9781337408332

Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Publisher:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr

Chapter20: Viruses, Bacteria, And Archaea

Section: Chapter Questions

Problem 3DAA: Bacteriophage-Inspired Antibiotics Although bacteriophages have been infecting bacteria for billions...

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Bacteriophage-Inspired Antibiotics Although bacteriophages have been infecting bacteria for billions of years, no mechanism, has evolved in bacteria to prevent the viruses from lysing the cell walls of their hosts. Now, scientists are targeting the same bacterial wall components that bacteriophages do. The goal is to develop antibiotics that bacteria will be less likely to develop resistance to. FIGURE 20.22 shows the results of a study to test Epimerox, a new bacteriophage-inspired antibiotic, against Bacillus anthracis, the bacterial species that causes the disease anthrax. FIGURE 20.22 Effect of Epimerox on the survival of mice with anthrax. Mice were infected with the bacteria B. anthracis. One group of 15 then began receiving a drug-free buffer solution 3 hours later. Another 15 were treated with Epimerox beginning 3 hours after infection. A third group of 15was treated with Epimerox beginning 24 hours after infection. In studies with Bacillus anthracis cells grown in culture, no Epimerox-resistant cells were observed. Explain why this result is consistent with the scientists' goal for developing this drug.
Bacteriophage-Inspired Antibiotics Although bacteriophages have been infecting bacteria for billions of years, no mechanism, has evolved in bacteria to prevent the viruses from lysing the cell walls of their hosts. Now, scientists are targeting the same bacterial wall components that bacteriophages do. The goal is to develop antibiotics that bacteria will be less likely to develop resistance to. FIGURE 20.22 shows the results of a study to test Epimerox, a new bacteriophage-inspired antibiotic, against Bacillus anthracis, the bacterial species that causes the disease anthrax. FIGURE 20.22 Effect of Epimerox on the survival of mice with anthrax. Mice were infected with the bacteria B. anthracis. One group of 15 then began receiving a drug-free buffer solution 3 hours later. Another 15 were treated with Epimerox beginning 3 hours after infection. A third group of 15was treated with Epimerox beginning 24 hours after infection. What do these data indicate regarding the optimal time to begin Epimerox treatment?
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?
7. Replication factor C plays which of the following roles in eukaryotic DNA replication?A. the sliding clampB. the clamp loaderC. the DNA ligaseD. a single-stranded DNA binding proteinE. a cofactor required for activating the DNA polymerase 8. Phages that program the host cell for continued particle releasing without killing the cell are called ____________ phages.A. lyticB. lysogenicC. temperateD. chronicE. none of the above 9. Retroviruses use _______ to make a DNA copy of their RNA genome.A. restriction enzymesB. DNA polymerase IC. RNA polymerase IID. reverse transferaseE. reverse transcriptase
After DNA replication, a eukaryotic chromosome ______. a. consists of two sister chromatids b. has a characteristic X shape c. is constricted at the centromere d. all of the above
Bacteriophages kill their host quickly by ______ . a. binary fission b. a lytic pathway c. a lysogenic pathway d. transformation
The spindle attaches to chromosomes at the _______. a. centriole b. contractile ring c. centromere d. centrosome
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.
Experimentally, when an E. coli bacterium already has a λ prophageintegrated into its chromosome, another λ phage cannot usually infectthe cell and establish the lysogenic or lytic cycle. Based on yourunderstanding of the genetic regulation of the phage λ reproductivecycles, why do you think the other phage would be unsuccessful?
Certain environmental conditions such as exposure to UV light areknown to activate lysogenic λ prophages and cause them to progressinto the lytic cycle. UV light initially causes the repressor protein to be proteolytically degraded. Make a flow diagram showing the subsequent events that lead to the lytic cycle. (Note: The xis gene codes for an enzyme that is necessary to excise the λ prophage from the E. coli chromosome. The enzyme integrase is also necessary for this excision.)
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?
Describe it asap don't copy "*!