Pyrimidine sequences from the DNA of bacteriophages fd, fl, and phi X174.

By the use of techniques previously developed to determine the sequence of large, unique pyrimidine oligonucleotides in bacteriophage fd DNA, pyrimidine sequences in the related phage fl and the unrelated phage varphiX174 amber 3 were determined. The DNA of fl contains many pyrimidine sequences completely identical to those in fd, including one sequence of 20 base residues. The large pyrimidine oligonucleotides in varphiX174 DNA are quite different from those in fd, although some homology is observed. There is present in each of the phage DNAs a pyrimidine oligonucleotide rich in thymidine that contains a common sequence of C_T_T_T_T_T_T_T.