Info

9. A plasmid that can replicate in E. coli and Pseudomonas is most likely a/an.

A. broad host range plasmid.

B. self-transmissible plasmid.

C. high-copy-number plasmid.

D. essential plasmid.

E. low-copy-number plasmid.

10. The frequency of transfer of an F' DNA molecule by conjugation is closest to the frequency of transfer of.

A. chromosomal genes by conjugation.

B. an F plasmid by conjugation.

C. an F plasmid by transformation.

D. an F plasmid by transduction.

E. an R plasmid by DNA transformation.

Applications

1. Some bacteria are more resistant to UV light than other bacteria. Discuss two reasons why this might be the case. What experiments could you do to determine whether each of the two possibilities could be correct?

2. A pharmaceutical researcher is disturbed to discover that the major ingredient of a new drug formulation causes frameshift mutations in bacteria. What other information would the researcher want before looking for a substitute chemical?

Critical Thinking

1. You have the choice of different kinds of mutants for use in the Ames test to determine the frequency of reversion by suspected carcinogens. You can choose a deletion, point mutation, or a frameshift mutation. Would it make any difference which one you chose? Explain.

2. You have isolated a strain of E. coli that is resistant to penicillin, streptomycin, chloramphenicol, and tetracycline. You also observe that when you mix this strain with cells of E. coli that are sensitive to the four antibiotics, they become resistant to streptomycin, penicillin, and chloramphenicol but remain sensitive to tetracycline. Explain what is going on.

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