Question

Match List I with List II:

Choose the correct answer from the options given below:

• A. A-V, B-IV, C-III, D-I
• B. A-IV, B-V, C-II, D-III
• C. A-I, B-II, C-III, D-IV
• D. A-III, B-I, C-IV, D-II

Hint:

Remember: Avery = Biochemical proof; Hershey-Chase = Unequivocal proof; Franklin = Physical structure; Chargaff = Base pairing logic.
Often, matching just two prominent pairs like A-V and D-I allows you to identify the correct option immediately in competitive exams.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question focuses on the historical landmarks and key scientists who contributed to the discovery of the structure and function of DNA as genetic material.
It requires matching specific experimental concepts or techniques with the researchers associated with them.
Detailed Explanation:

• Transforming Principle (A - V):
In 1928, Frederick Griffith discovered the "transforming principle" in Streptococcus pneumoniae.
Later, in 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty conducted biochemical characterization.
They purified DNA, RNA, and proteins from heat-killed S-strain bacteria to see which could transform R-strain into S-strain.
Only DNA was found to be the transforming substance, proving DNA is the genetic material.

• T2 Bacteriophage (B - IV):
Alfred Hershey and Martha Chase (1952) used the T2 bacteriophage (a virus that infects bacteria) to settle the debate between DNA and protein.
They labeled viral DNA with radioactive Phosphorus ($^{32}$P) and viral protein with radioactive Sulfur ($^{35}$S).
The experiment showed that only $^{32}$P entered the bacterial cells, confirming that DNA is the hereditary material passed from viruses to bacteria.

• X-ray Diffraction (C - III):
Rosalind Franklin and Maurice Wilkins used X-ray crystallography to study the structure of DNA.
Franklin produced "Photo 51," which was a high-resolution X-ray diffraction image of DNA.
This data provided critical clues about the helical nature, width, and periodicity of the DNA molecule, which were essential for Watson and Crick to build their model.

• Base Ratio (D - I):
Erwin Chargaff formulated "Chargaff's Rules" based on his quantitative analysis of DNA from different species.
He observed that the amount of Adenine is always equal to Thymine (\(A = T\)) and the amount of Guanine is always equal to Cytosine (\(G = C\)).
This discovery of specific base ratios was the fundamental evidence for base pairing in the double helix.

Step 2: Final Answer:
Matching the pairs: A matches with V, B with IV, C with III, and D with I.
This corresponds to Option (A).