Discuss why it is difficult to trace the origins of viruses and why they are important.
What will be an ideal response?
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When DNA replication begins, _____
a. the two DNA strands unwind from each other b. the two DNA strands condense for base transfers c. two DNA molecules bond d. old strands move to find new strands e. the sugar phosphate backbone is degraded
Which mechanism can be used to repair UV damage in Drosophila but not in humans?
What will be an ideal response?
An explanation for a biological process that is substantiated by a large body of evidence is called a
A. reductionism. B. prediction. C. hypothesis. D. systems biology. E. theory.
Figure 42.11
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Use the figure above showing human embryonic developmental day 14 to answer the following question.
Which of the following structures represents the yolk sac?
A. A B. B C. C D. D E. E