DNA Structure and Replication
The rapid appearance of HIV-1 strains that are resistant to AIDS drugs is due in part to which of the following property of its reverse transcriptase?

The RNase H domain of p66 causes error prone synthesis
AZT (zidovudine) is too expensive to be taken in effective doses
It lacks a proofreading exonuclease
It has low affinity for the correct dNTP's

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DNA Structure and Replication
The higher order structure of DNA shows symmetry, whereas the higher order structures of most proteins do not. Why isn't protein shape more regular like DNA?

Some S amino acids cause proteins to bend; others cause protein to flatten.
The many different amino acid R groups on proteins confer many different shapes.
DNA has one main function in cells whereas proteins have many.
All of these

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DNA Structure and Replication
Taylor, Woods and Hughes labeled Vicia DNA by allowing new DNA synthesis in the presence of radioactive thymine. After DNA replication (S phase of the cell cycle), it was observed that

neither chromatid was labeled
both (a) and (b)
only one chromatid of a chromosome was labeled
both chromatids of a chromosome were labeled

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