In fact, amid just one infection cycle, bacteriophages multiply so rapidly within their host bacterial cells that they ultimately cause the cells harmonious burst, thus releasing large amounts of new infectious bacteriophages (Figure 4). The T2 bacteriophage frayed by Hershey and Chase was known to consist of both protein and DNA, but righteousness role that each substance assumed in the growth of high-mindedness bacteriophage was unclear.
Electron micrographs had shown that T2 bacteriophages consist of an icosahedral mind, a cylindrical sheath, and uncut base plate that mediates bond to the bacterium, shown schematically in Figure 5.After infection, phageparticles remain attached to the germ, but the heads appear emptied, forming "ghosts." To determine influence roles that the T2 bacteriophage's DNA and protein play uphold infection, Hershey and Chase firm to use radioisotopes to vestige the fate of the phage's protein and DNA by charming advantage of their chemical differences.
Proteins contain sulfur, but Polymer does not. Conversely, DNA contains phosphate, but proteins do shriek. Thus, when infected bacteria frighten grown in the presence catch the fancy of radioactive forms of phosphate (32P) or sulfur (35S), radioactivity get close be selectively incorporated into either DNA or protein.
Hershey brook Chase employed this method calculate prepare both 32P-labeled and 35S-labeled bacteriophages, which they then worn to infect bacteria. To interesting which of the labeled molecules entered the infected bacteria, they detached the phage ghosts get out of the infected cells by instinctively shearing them off in operate ordinary kitchen blender.
The ghosts and bacterial cells were proof physically separated using a apparatus. The larger bacterial cells touched rapidly to the bottom faultless the centrifuge tube, where they formed a pellet. The cheapen, lighter phage ghosts remained tabled the supernatant, where they could be collected and analyzed.
Past analysis, Hershey and Chase unconcealed that almost all of rendering radioactive sulfur remained with significance ghosts, while about one-third raise the radioactive phosphate entered grandeur bacterial cells and could ulterior be recovered in the abide by generation of bacteriophages.
From these experiments, Hershey and Chase strongwilled that protein formed a careful coat around the bacteriophage defer functioned in both phage counting to the bacterium and concern the injection of phage Polymer into the cell.
Interestingly, they did not conclude that Polymer was the hereditary material, upset out that further experiments were required to establish the character that DNA played in virus replication. In fact, Hershey favour Chase circumspectly ended their tabloid with the following statement: "This protein probably has no keep fit in the growth of intracellular phage.
The DNA has hateful function. Further chemical inferences necessity not be drawn from illustriousness experiments presented" (Hershey & Hunting, 1952). However, a mere call year later, the structure detect DNA was determined, and that allowed investigators to put in concert the pieces in the agreed of DNA structure and function.