Question

Experiments by Avery, Mcleod, and McCarty supported DNA as the genetic material by showing that:
A. Both protein and DNA samples provided the transforming factor.
B. DNA was not complex enough to be the genetic material.
C. Only samples with DNA provided the activity.
D. Even though DNA was molecularly simple, it provided adequate variation to act as the genetic material.

Answer 1

Hint: The Avery-MacLeod-McCarty experiment was a 1944 experimental representation by Oswald Avery, Colin MacLeod, and Maclyn McCarty that DNA is the substance responsible for bacterial transformation, at a period during which it was widely assumed that proteins carried hereditary data (with the term protein as it's own conceptualized to imply a perception that its function is indeed primary).

Complete Step by Step Answer:
Their investigation was the outcome of research at the Rockefeller Institute for Medical Research in the 1930s and early twentieth century to purify and characterise the "transforming principle" liable for the transformation occurrence initially explained in Griffith's experiment. Griffith's experiment, published in 1928, discovered that certain "transforming principles" in pneumococcal bacteria can change their type.
Smooth colonies with a polysaccharide capsule that stimulates antibody formation characterise Pneumococcus; the distinct types can be divided thus according to their immunological specificity.

Avery's purification method involved initially massacring the bacteria with heat and then obtaining the saline-soluble components. The protein was then precipitated with chloroform, and the polysaccharide capsules have been hydrolysed with an enzyme. Immunological precipitation generated by type-specific antibodies was utilized to confirm the capsules' utter annihilation. The active part then was precipitated out via alcohol fractionation, yielding fibrous strands which could be eliminated with a stirring rod.
The proportional distribution of carbon, hydrogen, nitrogen, and phosphorus in this active portion was found to be consistent with the chemical components of DNA. Avery and his coworkers utilized a variety of biochemical tests to illustrate that the transformation was prompted by DNA instead of a small quantity of RNA, protein, or another cell component. They discovered that trypsin, chymotrypsin, and ribonuclease (enzymes that break down proteins or RNA) seemed to not affect it, however, an enzyme preparation of "deoxyribonucleic depolymerase" (a crude preparation drawn from different animal sources which might break down DNA) destructed the extract's transforming potential. Thus, samples consistent with DNA provided the activity.

Hence, the correct option is C


Note: This experiment demonstrates that genetic information should always be stored on DNA because R-cells require information from S-cells to construct a mucus capsule, i.e. to become S-cells. It is also to be noted that the DNA allowed R cells to be transformed into S cells.