ON THE SPECIFICITY OF DNA POLYMERASE

Abstract
For phage T4 rII transition mutants, the spontaneous reversion indices were generally much higher for G-C than A-T pairs. When a temperature-sensitive marker for DNA polymerase was crossed into these strains, the spontaneous reversion indices increased about the same for both base pairs. This indicates that the normal polymerase rejects noncomplementary base pairs (of normal DNA bases) much more effectively than the mutant polymerase. Both the normal and the mutant polymerase strains showed the same rate of rII reversion induction by all agents used. The DNA polymerase recognizes the position and structure of the sugar phosphate groups of the incoming deoxynucleotide triphosphate but not the structure of the individual bases: the correct base pairing is probably achieved by H bonding of the bases followed by rejection of incorrectly paired deoxynucleotide triphosphates by the DNA polymerizing enzyme(s).

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