The Transformation Experiment Conducted By T. Morgan

1.How did the work of TH morgan and company contribute to the eventual discovery that DNA was the genetic material in the cell?
T.H Morgan and his group proved that genes exist as part of chromosomes and that DNA and proteins were the makeup of chromosomes. This helped narrow the search for what made up genetic material especially because at the time little was known about nucleic acids and that their physical and chemical properties seemed to uniform to have a vast number/different traits inherited by every organism. Morgan started experimenting on bacteria viruses that infect them to further gather information on genetic material.

2.Explain the transformation experiment conducted by Frederick Griffith. What did the results of the experiment
Griffith had two strains of bacterium, one pathogenic (III-S) and one non pathogenic (II-R). The mice injected with pathogenic died and the mice injected with the non pathogenic cells were alive and healthy. Pathogenic cells that were heated treated were injected into the mice and did not cause harm. However, when the heat treated pathogenic cells were mixed with non pathogenic cells caused some of the living cells to become pathogenic. The new trait of pathogenicity was inherited by all the descendants of the transformed bacteria. Some chemical component of the dead cells caused a heritable change. The experiment suggested that it is possible for a change in genotype and phenotype due to the assimilation of external DNA of the cell (basically that dna can transform)

3.Explain how the work of Avery, McCarty, and MacLeod expanded on the work done by Griffith. What did the results of their experiment suggest?
Avery, McCarty, and MacLeod expanded the work done by Griffith by taking the heat treated pathogenic solution and breaking it down. They exposed the R strain (non pathogenic) to the purified S (pathogenic) strain and concluded that the DNA in the S strain is what is causing the transformation to occur. This came with skepticism because some still did not understand how DNA could carry genetic
coli cells. They asked which part of the virus is responsible to enter the E. coli cell during infection, DNA or protein? In their experiment, they used radioactive isotopes to tag phage DNA (radioactive phosphorus) and protein (radioactive sulfur) because protein contains sulfur and DNA contains phosphorus hence the reason behind the radioactive isotopes. They then allowed separate samples of nonradioactive E. coli cells to be infected by the protein and DNA labeled batches of T2. Then they tested to see which type of molecule entered the cell based on its label. Hershey and Chase found out that the DNA entered the host cell but the protein did not. The bacteria was returned to a culture medium which resulted in the infection continuing to run, but the E. coli released phages that contained radioactive phosphorus which concluded further that DNA carried genetic information through the cell to transform the previous viral chain to a new inherited viral chain, caused by DNA. This experiment demonstrated that DNA was the genetic material of bacteriophages because of its ability to transform the virus via genetic information and that DNA is what entered the host to infect the bacteria instead of the