Coordinate variation in density and recombination potential in T4 phage particles produced at different times after infection.

FREQUENCIES of recombinants in phage crosses depend not only on the genetic markers under observation but also on the time of lysis (DOERMANN 1953), conditions of phage growth (HERSHEY 1958; SYMONDS 1962), multiplicity of infection (TRAUTNER 1960; MOSIG 1962), and, apparently, unknown variables (HERSHEY 1958). Information about the sources of these variations may provide additional clues to the mechanism of recombination. Do individual differences in the phage particles crossed affect recombination frequency? The results reported here show that recombination frequencies depend on the time of matura-tion, during the previous growth cycle, of the phage particles entering into the cross. The relevant variable seems to be the DNA content of the particles.