In the late 1800s, Louis Pasteur was searching for a vaccine for anthrax in livestock. One French veterinarian had a local reputation for being able to cure anthrax by applying oils and wrapping the animal in cloth to induce a fever. Pasteur also knew that some animals got well on their own when left untreated. Pasteur tested the effectiveness of the local veterinarian's methods by injecting four cattle with anthrax bacteria. He then directed the veterinarian to perform his procedures on two cattle. The other two cattle were left alone. What is the rationale for Pasteur's experimental design?
(a). Two cattle represent a test of the veterinarian's hypothesis; two represent a test of Pasteur's hypothesis.
(b). Two cattle represent a test of the treatment; two serve as a control to determine the likelihood of survival without treatment.
(c). Two cattle represent a test based on inductive reasoning; two serve to test deductive reasoning.
(d). The two cattle that are treated are the only test being conducted; the other two cattle serve no purpose beyond representing all the untreated cattle in France.
(e). The two cattle not being treated were just a whim on Pasteur's part.
(b). Two cattle represent a test of the treatment; two serve as a control to determine the likelihood of survival without treatment.
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A muscle fiber contracts by a sequence of events initiated by the binding of acetylcholine to its receptor. Which of the following is the correct sequence?I - The calcium-troponin complex pulls tropomyosin away from the myosin-binding sites of actin.II - The freed-sites of actin bind to myosin to form cross-bridges.III - Calcium ion binds to the troponin.
A. I, II, and III B. III, II, and I C. I, III, and II D. II, III, and I E. III, I, and II
Restriction enzymes
A. cut only single-stranded DNA molecules. B. can cut randomly along a double-stranded DNA molecule. C. cut DNA molecules at specific sites. D. cut only single-stranded RNA molecules. E. function in DNA replication.
Your patient was admitted for a gunshot wound about a week ago. As a precautionary activity, the doctor placed her on antibiotics for a few days while recuperating. Blood specimens are drawn on the patient a several times daily and sent to the microbiology lab for analysis of bacteria. Nothing has grown in culture. On her 4th day in the hospital, she has had no fever and no other signs of infection, but one set of blood specimens has been reported positive for a bacterium. The culture was identified by the lab as Staphylococcus epidermidis, a common organism on the skin. Predict the likely situation leading to this.
A. The patient is immunodepressed and very susceptible to bacterial infection. B. Staphylococcus epidermidis is a skin contaminant that ended up in the blood specimen as a consequence of poor aseptic technique during the venipuncture. C. Staphylococcus epidermidis has converted to a pathogen because of the antibiotics prescribed for the patient. D. Staphylococcus epidermidis is a very slow growing bacterium and was probably in the blood right after the gunshot wound, but failed to grow until now.
Which of the following is not true of specialized transduction?
A. The phage genome retains the full complement of phage genes. B. It is restricted to those genes on either side of an integrated prophage. C. It is carried out by temperate phage. D. All of the choices are correct.