Discovery of DNA Experiments (Frederick Griffith (Griffith's…
Discovery of DNA Experiments
Griffith's experiment was called the "transforming principle"
To begin, Griffith tested both rough pneumonia (IIR) and smooth pneumonia (ISS) on mice to see whether they would survive or not.
Griffith first tested IIR and the mice survived with no bacteria recovered.
Griffith then tested the IIS which had a sort of capsule on it that made it difficult for the immune system to identify the pneumonia. This thus made it deadly to mice and they did not survive.
Griffith then boiled IIS which killed the bacteria and then Griffith tested the boiled IIS on the mice. And the end results was the survival of the mice and no trace of the bacteria.
The for the last part of the experiment Griffith tested both the boiled IIS and IIR. The results were shocking since the experiment ended to be lethal to the mice and there was bacteria recovered.
When Griffith exposed heat-killed pathogenic bacteria to harmless bacteria, some harmless were converted to disease-causing bacteria. This allowed Griffith to hypothesis that the transforming agent was a "ISS" protein
This experiment was on the right track of discovering how DNA was indeed genetic material and led to the race to find what the true transforming factor was which leads to Hershey and Chase's experiment.
Alfred Hershey and Martha performed an experiment dealing with E.Coli to see if phages' abilities to reprogram bacteria cells was due to their proteins or DNA. They set up two replicates and labeled the DNA with 32p and the protein with 35S
They first infected the bacteria E.Coli with two types of labeled T2.
Then Hershey and Chase did a second experiment showed DNA to be genetic material of T2.
Then Hershey and Chase took the 32p DNA and then blended it briefly. Then it was revealed that radioactivity was in the host and passed on to phage progeny.
Then they infect E.Coli and grow 35S-containing medium. The offspring then lysis with 35S-labeled protein.
And finally Hershey and Chase took 35S and blended it briefly. Then it was revealed that the radioactivity was in the phage ghosts and not passed onto the progeny.
Then they infect E.Coli and grow in 32p-containing medium. The offspring then lysis with 32p DNA
Then they prepared radioactivity labeled T2 bacteriophage
Once the experiment was over, both Hershey and Chase agreed that it was viral DNA that contains the instructions for making phages.
This experiment was important because it showed that