On the Replication of Desoxyribonucleic Acid (DNA)

Abstract

The discoveries of Hershey and Chase concerning the role of DNA in transmitting genetic information in phage and of Watson and Crick concerning the structure of DNA have brought the problem of the replication of DNA into focus. The structure proposed by Watson and Crick consists of two polynucleotide chains wound helically around a common axis, tied together by hydrogen bonds between the purine and pyrimidine side chains. These side chains of the two chains are arranged so that adenine is always matched with thymine and guanine with cytosine. The sequence of bases along either chain is not subject to any restrictions, but once the sequence along one chain is given, the sequence along the other chain is completely determined. This sequence, then, constitutes the genetic information, a linear message written in a four-symbol code. The duplex of the two chains contains the information in a twofold redundance. Each chain has a directional polarity because of the nonequivalence of the 3- and 5-positions through which each pentose is linked to the preceding and the following phosphate group in the chain. This polarity runs in opposite directions in the two chains of the duplex.

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