1. The change of R-form bacteria into S bacteria is known as

a. protein synthesis
b. translation
c. the transforming principle
d. the conjugating principle

2. Oswald Avery used different types of enzymes in his experiments to denature molecules including proteins and DNA. This way, he could determine which one was the “transforming principle”. What was he able to conclude?

a. DNase, which was used to degrade DNA, prevented transformation
b. neither protease or DNase was able to prevent transformation
c. enzymes that degraded the proteins, proteases, prevented transformation

3. What reason best illustrates why Hershey and Chase chose to use viruses in their experiment?

a. viruses are immune to radioactivity and cannot be degraded by it
b. viruses are made up of the two things that scientists were studying at the time, proteins, and DNA
c. viruses are easy to obtain and manipulate
d. viruses cannot make humans sick, but bacteria could

4. The experiment performed by Fredrick Griffith in the 1920s demonstrates that

a. all of the above
b. proteins contain genetic material responsible for infection
c. both the R-form and the S-form of the bacteria are virulent.
d. bacteria are capable of undergoing gene transfers

5. In one part of experiment, Hershey and Chase used radioactive phosphorus to label DNA in their T2 bacteriophages. What conclusion did they come to as a result?

a. they found radioactive phosphorus in the liquid medium, leading them to believe that DNA was not the genetic material
b. radioactive phosphorus did not transfer into the bacteria, leading them to continue their investigations and radioactive sulfur
c. they found radioactive phosphorus in the bacteria, leading them to believe DNA was the genetic material

c. transforming principle
a. DNase, which was used to degrade DNA, prevented transformation.
b. viruses are made up of the two things that scientists were studying at the time, proteins, and DNA.
d. bacteria are capable of undergoing gene transfers.
c. they found radioactive phosphorus in the bacteria, leading them to believe DNA was the genetic material.

Explanation:

Frederick Griffith's Experiment of 1928:

Frederick Griffith, a British bacteriologist discovered DNA to be the genetic material by conducting an experiment.

Griffith took two bacterial strains: S strain (virulent, deadly) and R strain (non-virulent).

Griffith injected four groups of mice with four different concoctions of bacteria:

When Griffith observed all the solutions, he made some shocking observations:

Griffith observed that the heat killed S-strain did not kill the mice.
The mixture of R and heat killed S strains did.
When he examined and cultured the dead mice, he found out that they contained live S-strain bacteria.

This indicated a transfer of genetic material between R and S strains, leading to the death of the mice.
He called the genetic material the transforming principle.

Avery, McCarty, and MacLeod Experiments:

Avery, McCarty, and MacLeod performed biochemical tests on cultures of heat killed S bacteria to identify the transforming principle proposed by Griffith.
They observed that the biochemical tests for protein were negative, those for DNA were positive. The DNase, RNase tests concluded that the transforming principle was DNA as DNase containing samples did not have any S-strain bacteria and thus, prevented transformation.

Hershey and Chase Experiment:

Hershey and Chase conducted experiments to identify whether the DNA or protein was the transforming principle.
They cultivated bacteriophages with radioisotopes of sulfur and phosphorous separately.
They later infected bacteria with the bacteriophages and made the following observations:
After purification and centrifugation of the samples, they concluded that the P32 isotope appeared in the pellet. This indicated that DNA contained P32 and was the transforming principle.
As protein separates in the supernatant, they observed that the sulfur radioisotope appeared in the supernatant.