II. Cross Hybridization and Rate of Chain Elongation of the Two Classes of DNA Intermediates

Abstract

IN the preceding paper¹ it was shown that under inhibition of polynucleotide ligase by NMN two classes of DNA pieces accumulate during in vitro Escherichia coli DNA synthesis. They consist of newly synthesized material and appear in equal amounts. It was assumed that the short pieces are copies of the parental strand which cannot be copied continuously by a polymerase with a 3′–5′ activity whereas the long pieces originate from the opposite parental strand which could in principle be copied continuously. If this is true neither the short pieces nor the long pieces should be able to hybridize among themselves, whereas the long pieces should hybridize with the short pieces. We present hybridization data showing complementarity between the population of long pieces and that of short pieces and no complementarity within the single populations. We also show that the long and the short pieces are polymerized at 25° C at approximately in vivo rate.