Genome Of Recipient Cells Research Articles

Fate of exogenous mouse DNA in chicken fibroblasts in vitro: Non-conservative preservation

Monolayers of chicken embryo cells were cultivated for 24 h in the presence of mouse [ 3H]DNA and bromo[ 14C]deoxyuridine. The cells were lysed and subjected to CsCl density gradient analysis. Newly synthesized cellular DNA was both density and 3H labeled, and banded in two peaks formed, respectively, by “heavy-light” and “heavy-heavy” stranded molecules whose 3H label corresponded to donor DNA reutilized at the precursor level. A significant amount of donor DNA, equivalent to 2 % of the recipient cell genome, escaped degradation in the recipient cell environment and banded in the region of light density. This DNA, rebanded under alkaline conditions, showed a shift towards higher density, proving that density label was introduced into extant donor DNA strands. The shift was lacking when bromodeoxyuridine-prelabeled recipient cells were incubated with donor DNA in the absence of density label. Thus, donor DNA molecules did not attach end-to end to recipient DNA. The formation of non-conservative material being associated with the recipient cell DNA synthesis suggests that recombination events took place between donor and newly synthesized recipient DNA strands.

STUDIES ON THE MECHANISM OF RADIATION INACTIVATION OF MICRO‐ORGANISMS—IX. MECHANISM OF THE ULTRAVIOLET‐INDUCED INACTIVATION OF TRANSFORMING DEOXYRIBONUCLEIC ACID

SummaryPurified transforming DNA and whole cells of Haemophilus influenzae were exposed to ultraviolet radiation. The DNA and the cells carried three linked antibiotic‐resistant markers.Inactivation of these markers, singly and in all possible combinations proceeded semilogarithmically with U.V. dose. The in vitro and in viva pictures were quite alike.Experiments designed to test the possible integration of U.V. damaged DNA regions into the genome of recipient cells demonstrated that the bulk of these regions is rejected by the cells. The “inactivation” of genetic markers as scored by the transformation reaction is thus simply due to their location on such regions. They need not be damaged themselves.U.V.‐induced DNA damage seemed to induce double recombination events in the transformation process.