Recombination Intermediates Formed in the Extract from T7-infected Cells

Excerpt

One of the useful approaches toward understanding the molecular mechanism of genetic recombination of bacteriophage is to isolate and characterize intermediates in the recombination process. Phage T7 has suitable characters for such approach; the genome, 2.5 × 10⁷ daltons (Freifelder 1970), is small enough to be isolated as an intact DNA molecule; T7 exists in infected cells in simple linear monomeric form in the absence of DNA replication (Wolfson et al. 1972); and the efficiency of recombination is as high as those of T-even phages (Studier 1969). Moreover, many mutants of phage T7 have been isolated (Hausman and Gomez 1967; Studier 1969) and several genes involved in DNA repHcation and genetic recombination have been identified (Studier 1969; Powling and Knippers 1974; Kerr and Sadowski 1975).

With phage T4, Tomizawa and Anraku (1964) found that the early process of recombination is separable from replication. Their methods allow analyses of DNA molecules...