Based on the context given below, answer the following questions:

DNA in eukaryotes is a double-helical structure with two anti-parallel strands intertwined equidistantly. The double-helical structure was deciphered by James Watson and Francis Crick on the basis of X-ray diffraction studies. The hydrophilic backbones of alternating sugar and phosphate groups are on the outside of the helix held together by phosphodiester bonds. The purine and pyrimidine bases of both the strands are stacked inside the double helix. Adenine binds with thymine with hydrogen bond and cytosine binds with guanine with hydrogen bond. The DNA is transcribed into messenger RNA, ribosomal RNA and transfer RNA. Messenger RNA is translated into protein in the cytoplasm.

Q73.X-ray diffraction experiment to analyze the structure of DNA was performed by

1. James Watson and Francis Crick

2. Rosalind Franklin and Maurice Wilkins

3. Tom Cech and Sidney Altman

4. Martha Chase and Alfred Hershey

   The correct answer is Rosalind Franklin and Maurice Wilkins.

   X-ray Diffraction DNA Analysis

   Rosalind Franklin performed the landmark X-ray diffraction experiments on DNA fibers at King’s College London, producing “Photo 51” (1952) that revealed the double helix’s key parameters: helical X-pattern, 3.4 Å base spacing, and uniform 2 nm diameter. Maurice Wilkins led her lab and shared this data with Watson and Crick, enabling their 1953 model.

   Option Analysis

   • James Watson and Francis Crick: Built the double-helix model using Franklin’s diffraction data—they interpreted, didn’t generate the X-ray results.

   • Rosalind Franklin and Maurice Wilkins: Correct—Franklin’s crystallography provided structural evidence; Wilkins supplied DNA fibers.

   • Tom Cech and Sidney Altman: Discovered ribozymes (catalytic RNA, Nobel 1989)—unrelated to DNA structure.

   • Martha Chase and Alfred Hershey: Proved DNA as genetic material via bacteriophage labeling (1952 blender experiment)—no X-ray work.

   Introduction: X-ray Diffraction Experiment to Analyze DNA Structure

   NEET molecular biology tests DNA discovery timeline through questions like “X-ray diffraction experiment to analyze the structure of DNA.” Rosalind Franklin and Maurice Wilkins provided the experimental data via Photo 51 that made Watson-Crick model possible. This clarifies contributions and eliminates common exam traps.

   Photo 51: The Crucial Evidence

   Franklin’s X-ray crystallography of hydrated B-DNA showed:

   • X-pattern: Helical structure confirmation

   • Meridional spots: 3.4 Å repeat (base pair stacking)

   • Layer lines: 34 Å turn distance
     Wilkins shared this May 1953 with Cambridge team.

   DNA Discovery Team Roles

   Scientists	Contribution	Year
   Franklin/Wilkins	X-ray diffraction data	1952
   Watson/Crick	Double helix model	1953
   Hershey/Chase	DNA = genetic material	1952
   Cech/Altman	Ribozyme discovery	1989

   Why Franklin/Wilkins for NEET?

   Context emphasizes “X-ray diffraction studies” as basis for model—points to experimenters, not model builders. Nobel 1962: Watson, Crick, Wilkins (Franklin died 1958).

   NEET Exam Strategy

   Trap avoidance: Model ≠ measurement. Photo 51 timeline precedes Nature paper.
   Mnemonic: “Franklin’s Photo Fuels Finding.”
   Related PYQs: Base pairing (A=T, G≡C), antiparallel strands.

   Key fact: Without diffraction data, no double helix—credit the physicists first.