Which of the following correctly describes the roles of Mg2+ ions in the polymerase reaction?
A. The first Mg2+ deprotonates the aspartate in the active site.
B. The first Mg2+ deprotonates the 3'-OH of the previous nucleotide.
C. The second Mg2+ deprotonates H2O in the active site.
D. The second Mg2+ stabilizes PPi by protonation.
E. None of these choices is correct.
B
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