TRANSFER DISTRIBUTION OF THE DNA OF T4 PHAGE OVER ITS PROGENY.

Abstract

The distribution of the DNA of bacteriophage T4 over progeny produced by an infection ofE. coli with32P-labeled, deuterated parent phages was ascertained by examining the density of the transferred DNA in intact progeny virus particles and in DNA molecules extracted from progeny or phage-infected cells. The following results were obtained: 1. Those progeny phage that contain the bulk of transferred parental32P derive approximately 10% of their DNA from the parent. This value is a weight average, but it can be estimated that most of the transferred parental32P appears in progeny whose DNA complement comprises no less than 7 and no more than 13% atoms of parental origin. 2. In control experiments involving non-deuterated T4 parent phage, the transferred parental DNA appears in phage particles that are less dense than the average progeny. This fact must be taken into account in the interpretation of transfer distribution experiments involving density labels. 3. After breakage of the progeny DNA molecule into small fragments less than 1% of its original size, all the transferred parental atoms are found to reside in fragments that contain 50% parental atoms. This result is consistent with the interpretation that these fragments are half parental — half newly synthesized hybrid DNA molecules generated by semi-conservative replication. 4. The fragmentation of the parental DNA molecule occurs early in the infective process, no later than the start of replication of the vegetative phage DNA.