Concept explainers
This question combines your knowledge of bacterial conjugation (described in Chapter 7) and the genetic regulation that directs the phage
reproductive cycles. When researchers mix donor Hfr strains with recipient
bacteria that are lysogenic for phag
conjugate with recipient
bacteria that do not contain any phag
into the lytic cycle. Based on your knowledge of the regulation of the two reproductive cycles of phage
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Genetics: Analysis and Principles
- When various strains of λ phage are seeded on a lawn of E. coli, they can form clear or turbid plaques. (b) For mutant λ phages that can only form clear plaques, give two different types of mutation in the phage that can explain the clear plaque phenotype.arrow_forwardAhmed had isolated bacteria from the sputum of a patient that seemed somewhat resistant to their antibiotic treatment, since multiple weeks of treatment had yielded no satisfactory improvement of their active disease. The researcher had then resuspended the patient's sputum in saline and used a mouse model to measure the efficiency of a phage selected for its capacity to target M. mycobacterium, as a single therapy, and as a combination therapy with antibiotics. Here is a schematic representation of the experiment: Group 1 Control (saline) Inoculate mice with patient sputum Group 2 wait for active Treated with phage disease to show Collect lung sample every 2 weeks Tuberculosis Sputum samples patient Group 3 Treated with Abx Group 4 Split mice showing active disease in 4 Treated with Abx and Count bacteria in sample groups phage Figure 4. Sputum from patients were isolated and resuspended in saline. Mice were given equal amounts of resuspended sputum intra-nasally and were left to…arrow_forwardAhmed had isolated bacteria from the sputum of a patient that seemed somewhat resistant to their antibiotic treatment, since multiple weeks of treatment had yielded no satisfactory improvement of their active disease. The researcher had then resuspended the patient's sputum in saline and used a mouse model to measure the efficiency of a phage selected for its capacity to target M. mycobacterium, as a single therapy, and as a combination therapy with antibiotics. Here is a schematic representation of the experiment: Group 1 Control (saline) Inoculate mice with patient sputum Group 2 wait for active disease to show Treated with phage Sputum samples Collect lung sample every 2 weeks Tuberculosis patient Group 3 Treated with Abx Split mice showing active disease in 4 Group 4 Treated with Abx and Count bacteria in sample groups phage Figure 4. Sputum from patients were isolated and resuspended in saline. Mice were given equal amounts of resuspended sputum intra-nasally and were left to…arrow_forward
- Ahmed had isolated bacteria from the sputum of a patient that seemed somewhat resistant to their antibiotic treatment, since multiple weeks of treatment had yielded no satisfactory improvement of their active disease. The researcher had then resuspended the patient's sputum in saline and used a mouse model to measure the efficiency of a phage selected for its capacity to target M. mycobacterium, as a single therapy, and as a combination therapy with antibiotics. Here is a schematic representation of the experiment: Group 1 Control (saline) Inoculate mice with patient sputum Group 2 wait for active disease to show Treated with phage Sputum samples Collect lung sample every 2 weeks Tuberculosis patient Group 3 Treated with Abx Split mice showing active disease in 4 Group 4 Treated with Abx and Count bacteria in sample groups phage Figure 4. Sputum from patients were isolated and resuspended in saline. Mice were given equal amounts of resuspended sputum intra-nasally and were left to…arrow_forwardBacteriophage lambda is integrated in DNA of a host cell, which is exposed to UV light in a body of water in the environment. Describe the sequence of events that occurs in its life cycle. Briefly describe the role of the Lambda repressor (cI) and cII activator to regulate the switch between the lysogenic and lytic cycles of phage Lambda.arrow_forwardDescribe how the lambda phage controls the lytic and lysogenic cycles. Include cro, cI, cII, and cIII in your description. Which of these proteins is responsible for the initiation of lysogeny or lytic pathways?arrow_forward
- Conjugation between an Hfr cell and 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.arrow_forwardWhat is the difference between the lytic and lysogenic cycle of bacteriophages? In the lysogenic cycle, the phage DNA integrates itself into the host genome after penetration, and continues to biosynthesis when conditions change The host cell is not killed in the lysogenic cycle The lytic cycle occurs in the nucleus, while the lysogenic cycle occurs in the cytoplasm In the lysogenic cycle, penetration is achieved through phagocytosisarrow_forwardIn Hershey-Chase experiment, bacteriophages protein coats were tagged with radioactive isotope S-32. These phages were used to infect E. coli cells and the cells were further centrifuged to form pellets. Why was the radioactivity level of S-32 found greater outside the cells compared to the E. coli cell pellets? Explain briefly. If the experiment is repeated in the same manner but this time the phage protein coats are labelled with isotope X and the phage DNA with isotope Y, which isotope’s radioactivity will be found in greater amounts in the E. coli cell pellets after centrifugation? Explain briefly.arrow_forward
- Eight mutant bacteriophage strains cannot lyse a certain type of bacteria that can be lysed by wild-type bacteriaphages. The mutant strains were allawed to infect the bacteria in a complementation test. A "+ indicates that lysis occurred with coinfection.Aindicates that lysis did not occur. GKWTMAQC G -++|+ ++l+ - K. - + - ++ +| + -+| - |-++ + + + M - + + + A cistron is defined by no complementation in the Ciş : configuration. Haw many genes are controlling lysis in this bacteriophage? (Use a number not a word in the space) 3 Which of the following strains below are defective in the same gene as strain Q? Answer yes if the strain is defective or no if it is not. Strain Defective A N/Aarrow_forwardDuring the lysogenic cycle of lambda (1) phage the phage genome is integrated in the host chromosome where it is passed on to daughter cells through binary fission. the phage DNA is copied and accumulates in the cytoplasm. Then a trigger causes capsid proteins to be made and phages are assembled. the product of one prophage gene is made and it activates most of the other prophage genes. the viral genes immediately turn the host cell into a lambda-producing factory. Then the host lyses. 0000arrow_forwardYou are given two strains of E. coli. The Hfr strain is arg+ ala+ glu+ pro+ leu+ T s; the F− strain is arg − ala− glu− pro−leu− T r. All the markers are nutritional except T, which determines sensitivity or resistance to phage T1. The order of entry is as given, with arg+ entering the recipient first and T slast. You find that the F− strain dies when exposed to penicillin (pens), but the Hfr strain does not (penr). How would you locate the locus for pen on the bacterial chromosome with respect to arg, ala, glu, pro, and leu? Formulate your answer in logical, well-explained steps, and draw explicit diagrams where possible.arrow_forward
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