Report of Progress, Year endins April 1, 1957.
Grant No. C-2158, A. D. Hershey, Carnezie Institution of Washington,
Cold Sprins Harbor, N. Y.
"Growth and Inheritance in Bacteriophage"

Our current work is based on the following facts previously reported.
(1) Bacteria infected with T2 synthesize in the presence of chloramphenicol DNA
that can combine with protein synthesized after the removal of chloramphenicol
to form phage particles. (2) Part of the DNA of phage particles inactivated
by ultraviolet light, when present in bacteria infected with unirradiated phage
particles, is incorporated into a very few noninfective particles among the
offspring.

The following facts have been demonstrated recently by J. Tomizawa, partly
by independent work in his laboratory in Tokyo, partly by work done since he
joined our group in February of this vear. (3) Bacteria irradiated with ultra-
violet light after infection produce dead phase particles in numbers dependent
on the amount of phase precursor DNA present in the cells at the time of irradia-
tion. (4) This is true equally whether such DHA is accumulated in the absence
or in the presence of chloramphenicol, In the latter case, the irradiated DIA
is incorporated into phage particles after removal of the antibiotic, and, if
the amount of irradiated DNA is sufficient, nearly all the particles formed are
dead. Such dead particles have properties similar to those produced by irradiat-
ine phage particles themselves,

Fact (2) we interpret to mean that irradiation produces lethal damages in
phage "chromosones" that contain only part of the phage DNA. If this is sos the
other facts can only mean that the multiplicative phase of phase srowth is
Synthesis of naked chromosomal DNA, which is incorporated into phare particles
only as a final act of phase growth by a process that is little affected by
radiation damage.

Experiments by J. iandell and =. Burgi in our laboratory are designed to
explore further the meaning of fact (2), but have not yet reached a decisive phase.

Further confirmation of the central genetic role of DNA is derived from the
following work of the principal investigator. Examination of constituents of
particlos of phage T2 that can be labéled by Cl4-earginine and Gl4-lysine reveal
only two previously undetected components, both minor. -One is an unidentified
amino acid present in the particles in the free state. The other is a peptide
containing mainly lysine, aspartic acid, and clutamic acid. This component is
not an integral part of the phase chromosome as shovm by its failure to transfer
from parental to offspring phages and by its failure to be synthesized torether
with phage precursor DIA in the presence of chloramphenicol. The latter blooks
synthesis of all types of protein equally.

Our work is closely related to but Coes not duplicate that of C. Levinthal,
University of Uichigan, A. Il. Doermann, University of Rochester, and G. S. Stent,
University of California at Berkeley.