Suppose that a DNA change results in the substitution of one codon for another, and the new codon specifies a stop codon where it did NOT previously. What type of mutation has occurred?
a. a nonsense mutation
b. a missense mutation
c. a chromosomal mutation
d. a silent mutation
Ans: a. a nonsense mutation
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You add an unknown phage to a mixture of F+ and F- cells of E. coli and plate out the bacteria. The bacterial colonies that grow are all F-. How can you explain this phenomenon?
A. The phage bound to a receptor on the sex pilus, and therefore only infected the F+ cells (leaving the F- cells alone). B. The phage bound to a receptor on the F- cells, leaving only them alive and allowing the F+ cells to die off. C. The phage integrated (lysogenized) the F- cells, giving them a selective advantage over the F+ cells. D. F+ cells are uniquely susceptible to phage attack for unknown reasons.
The enzyme that directly converts NADP+ to NADPH is
A. ferredoxin. B. NADP reductase. C. plastocyanin. D. RUBISCO. E. cytochrome complex.
What type of response is most associated with the brain sensing a cold environment? a. Decrease in blood flow to the skin
b. Heart rate decreasing. c. Increased respiration. d. Sweat glands increase their output. e. Increase in blood flow to the skin.
Mitotic cell division results in two identical cells by replicating the cell's DNA and then dividing .
A. None of the answer choices is correct. B. once; once C. twice; twice D. twice; once E. once; twice