Concept explainers
In a genetics lab, Kim and Maria infected a sample from an E. coli culture with a particular virulent bacteriophage. They noticed that most of the cells were lysed, but a few survived. The survival rate in their sample was about 1 × 10-4. Kim was sure the bacteriophage induced the resistance in the cells, while Maria thought that resistant mutants probably already existed in the sample of cells they used. Earlier, for a different
experiment, they had spread a dilute suspension of E. coli onto solid medium in a large petri dish, and, after seeing that about 105 colonies were growing up, they had replica-plated that plate onto three other plates. Kim and Maria decide to use these plates to test their theories. They pipette a suspension of the bacteriophage onto each of the three replica plates. What should they see if Kim is right? What should they see if Maria is right?
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Genetics: From Genes to Genomes
- A bacterial transformation is performed with a donor strain that is resistant to four drugs, A, B, C, and D, and a recipient strain that is sensitive to all four drugs. The resulting recipient cell population is divided and plated onmedia containing various combinations of the drugs. The following table shows the results.a. One of the genes is distant from the other three, which appear to be closely linked. Which is the distant gene? b. What is the likely order of the three closely linked genesarrow_forwardImagine that you are a student in Alfred Hershey and Martha Chase’s lab in the late 1940s. You are given five test tubes containing E. Coli bacteria infected with T2 bacteriophages that have been labeled with either 32P or 35S. Unfortunately, you forget to mark the tubes and are now uncertain about which tubes is which. You performed their blender experiment and got the following results. Which tube out of these 5 contains E. Coli infected with 32P-labeled phage? Explain your answer.arrow_forwardIn your laboratory, you have an F − strain of E. coli that is resistant to streptomycin and is unable to metabolize lactose, but it can metabolize glucose. Therefore, this strain can grow on media that contain glucose and streptomycin, but it cannot grow on media containing only lactose. A researcher has sent you two E. coli strains in two separate tubes. One strain, let’s call it strain A, has an F factor that carries the genes that are required for lactose metabolism. On its chromosome, it also has the genes that are required for glucose metabolism. However, it is sensitive to streptomycin. This strain can grow on media containing lactose or glucose, but it cannot grow if streptomycin is added to the media. The second strain, let’s call it strain B, is an F − strain. On its chromosome, it has thegenes that are required for lactose and glucose metabolism. StrainB is also sensitive to streptomycin. Unfortunately, when strains A and B were sent to you, the labels had fallen off the…arrow_forward
- A person with a rare genetic disease has a sample of her chromosomessubjected to in situ hybridization using a probe that is known to recognize band p11 on chromosome 7. Even though her chromosomes look cytologically normal, the probe does not bind to this person’s chromosomes. How would you explain these results? How would you use this information to positionally clone the gene that is related to this disease?arrow_forwardWhy is the observed mutation rate of E. coli 10–8 to 10–10 per base pair replicated, even though the error rates of Pol I and Pol III are 10–6 to 10–7 per base pair replicated?arrow_forwardA genetics instructor designs a laboratory experiment to study the effects of UV radiation on mutation in bacteria. In the experiment, the students spread bacteria on petri plates, expose the plates to UV light for different lengths of time, place the plates in an incubator for 48 hours, and then count the number of colonies that appear on each plate. The bacteria that have received more UV radiation should have more pyrimidine dimers, which block replication; thus, fewer colonies should appear on the plates exposed to UV light for longer periods. Before the students carry out the experiment, the instructor warns them that while the bacteria are in the incubator, the students must not open the incubator door unless the room is darkened. Why should the bacteria not be exposed to light?arrow_forward
- T. Miyake and M. Demerec examined proline-requiring mutations in the bacterium Salmonella typhimurium (). On the basis of complementation testing, they found four proline auxotrophs: proA, proB, proC, and proD. To determine whether proA, proB, proC, and proD loci were located close together on the bacterial chromosome, they conducted a transduction experiment. Bacterial strains that were proC+ and had mutations at proA, proB, or proD were used as donors. The donors were infected with bacteriophages, and progeny phages were allowed to infect recipient bacteria with genotype proC− proA+ proB+ proD+. The recipient bacteria werethen plated on a selective medium that allowed only proC+ bacteria to grow. After this, the proC+ transductants were plated on selective media to reveal their genotypes at the other three pro loci. The following results were obtained: Q.Which genotypes represent single transductants and which represent cotransductants?arrow_forwardT. Miyake and M. Demerec examined proline-requiring mutations in the bacterium Salmonella typhimurium (). On the basis of complementation testing, they found four proline auxotrophs: proA, proB, proC, and proD. To determine whether proA, proB, proC, and proD loci were located close together on the bacterial chromosome, they conducted a transduction experiment. Bacterial strains that were proC+ and had mutations at proA, proB, or proD were used as donors. The donors were infected with bacteriophages, and progeny phages were allowed to infect recipient bacteria with genotype proC− proA+ proB+ proD+. The recipient bacteria werethen plated on a selective medium that allowed only proC+ bacteria to grow. After this, the proC+ transductants were plated on selective media to reveal their genotypes at the other three pro loci. The following results were obtained: Q.Is there evidence that proA, proB, and proD are located close to proC? Explain your answer.arrow_forwardT. Miyake and M. Demerec examined proline-requiring mutations in the bacterium Salmonella typhimurium (). On the basis of complementation testing, they found four proline auxotrophs: proA, proB, proC, and proD. To determine whether proA, proB, proC, and proD loci were located close together on the bacterial chromosome, they conducted a transduction experiment. Bacterial strains that were proC+ and had mutations at proA, proB, or proD were used as donors. The donors were infected with bacteriophages, and progeny phages were allowed to infect recipient bacteria with genotype proC− proA+ proB+ proD+. The recipient bacteria werethen plated on a selective medium that allowed only proC+ bacteria to grow. After this, the proC+ transductants were plated on selective media to reveal their genotypes at the other three pro loci. The following results were obtained: Q.Why are there no proC− genotypes among the transductants?arrow_forward
- Suppose a 10-year old patient has come to your office with a very rare disease. One so rare that only 100 people for the past 100 years have been diagnosed and nobody knows the gene or genes that are mutated in this disease. Describe the gene sequencing toold you would use to identify the mutated gene or genes in this hypothetical disease.arrow_forwardIn a transformation experiment, donor DNA was obtained from aprototroph bacterial strain (a+b+c+), and the recipient was a tripleauxotroph (a-b-c-). What general conclusions can you draw aboutthe linkage relationships among the three genes from the followingtransformant classes that were recovered? a+ b- c- 180 a- b+ c- 150 a+ b+ c- 210 a- b- c+ 179 a+ b- c+ 2 a- b+ c+ 1 a+ b+ c+ 3arrow_forwardWhich of the following patterns was observed, in the experiments of Hershey and Chase, using the T2 bacteriophage of E. coli? radioactive proteins were passed on to viral progeny, but not radioactive polynucleotides radioactive polynucleotides were passed on to viral progeny, but not radioactive proteins both radioactive proteins and radioactive polynucleotides were passed on to viral progeny both radioactive polynucleotides and radioactive proteins were passed on to viral progeny neither radioactive proteins nor radioactive polynucleotides were passed on to viral progenyarrow_forward
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