The 5′-terminal dinucleotides of the separated strands of T7 bacteriophage deoxyribonucleic acid

Abstract

Selective labeling of the 5′-hydroxyl termini of DNA by polynuclcotide kinase has been used to study the 5′-terminal residues of T7 DNA. After separation and isolation, one strand of the duplex molecule was found to be terminated at its 5′-end by deoxyadenylate, and the complementary strand by deoxythymidylate. The 5′-terminal dinucleotides of T7 DNA were identified after hydrolysis of the DNA by exonuclease I from Escherichia coli. The results indicate that one strand is terminated by d-pApG and the other by d-pTpC.