Identifying the Genetic Material

Frederick Griffith, a bacteriologist, was stressful to prepare a vaccine against the pneumonia-causing bacterium, S. pneumoniae. A vaccine is a substance that is watchful from killed or weakened microorganisms and is introduced into the body to harbor the body against future infections by the microorganisms. griffon worked with 2 types, or trickles of S. Pneumonia. The first transmission line is enclosed in a wrap made of polysaccharides. The ejector seat protects the bacterium from the bodys demur systems this helps make the microorganisms virulent, or equal to coif disease.Because of the capsule, this strain of S. Pneumonia grows as smooth-edged (S) colonies when bighearted in a Petri dish. The second strain of S. Pneumonia lacks the polysaccharide capsule and does non cause disease. When grown in a Petri dish, the second strain forms rough-edged R colonies Griffith knew that mice infected with the S bacterium grew sick, and died, while mice infected with the R bacter ium were not harmed. To determine whether the capsule on the S bacterium were causing the mice to die, Griffith injected the mice with assassinated S bacterium. The mice remained healthy.Griffith then prepared a vaccine of weakened S bacteria by raising their temperature to a blockage at which the bacteria were change-killed meaning that they could no longer reproduce ( the capsule remained on the bacteria). When Griffith injected the mice with heat-killed S bacteria, the mice still holdd. Thus, Griffith knew it was not the capsule on the S bacteria that killed the mice. He then entangled the stainless live R bacteria with the harmless heat killed S bacteria. Mice injected with this mixture of previously harmless preparations died.When Griffith examined the blood of the dead mice, he rig that the live R bacteria had inevitable polysaccharide capsules. Somehow, the harmless R bacteria had changed and became virulent S bacteria. Griffith had discovered what is straight off called transformation, a change in phenotype cause when bacterial cells take up foreign familial material. But the cause of the transformation was not known at the time.A genuinelys experiments An elegant serial publication of experiments showed that the activeness of the material esponsible for transformation was not affected by protein-destroying enzymes, but the activity was stopped by a deoxyribonucleic acid- destroying enzyme. In this way, al well-nigh 100 years afterwards Mendels experiments were performed, Oswald Avery and his co-workers, biologists at the Rockefeller Institute, in NYC, demonstrated that deoxyribonucleic acid is the material responsible for transformation. desoxyribonucleic acid had the instruction manual for the making of the capsule in the S strain of S. Pneumonia. III. Hershey and Chase Show that computer virus Genes Are Made of DNA.Scientists knew that proteins were important to many an(prenominal) aspects of cell structure and metabolism, so most o f them suspected that proteins were the familial material. They likewise knew very little about DNA, so they could not imagine how DNA could exsert genetic nurture. A. Viruses reveal DNAs role Alfred Hershey, and Martha Chase, performed an experiment that colonised the controversy. It was known at the time that viruses, which were much simpler then cells, are made of DNA ( or sometimes RNA) surrounded by a protective protein coat.Bacteriophage, also referred to as phage are viruses that infect bacteria. It was also known that when phage are able to produce more viruses, which are released when the bacterial cells rupture. Hershey and Chase knew that the only molecule in the phage that contained phosphorus was its DNA. Likewise, the only phage molecules that contained sulfur were the proteins in it coat. Hershey and Chase used these differences in chemical composition to carry out the experiment.Steps T2 phages were grown with E. coli bacteria in a nutrient forte containing an y 35S or 32P E. oli were infected with either 35S- or 32P- labeled phages. The infected E. coli were mixed and then spun. Each spirit level was time-tested for radioactivity. The 35S label was be only in the upper layer containing the viruss parts. The 32P label was found mostly in the lower layer containing the E. coli. Upon infection, the phages protein coat falls away. They inject their DNA into the E. coli, causing the E. coli to make more viral DNA and proteins. These important experiments, and many others since, arouse shown that DNA is the molecule that stores genetic information in living cells.