Watson Crick model of DNA was proposed on the basis of
**Core Concept**
The Watson-Crick model of DNA describes the double helix structure of DNA, where two complementary strands of nucleotides are twisted together. This model explains how DNA replicates and transmits genetic information. The structure consists of sugar molecules (deoxyribose), phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, and thymine).
**Why the Correct Answer is Right**
The Watson-Crick model was proposed based on X-ray crystallography data obtained by Rosalind Franklin and Maurice Wilkins. The model describes the double helix structure with sugar-phosphate backbones on the outside and nitrogenous bases paired in the center. Adenine (A) pairs with thymine (T) through two hydrogen bonds, while guanine (G) pairs with cytosine (C) through three hydrogen bonds. This base pairing is crucial for maintaining the stability of the DNA double helix.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Watson-Crick model was not proposed based on the Chargaff's rules, which describe the base pairing rules but do not explain the three-dimensional structure of DNA.
**Option B:** This option is incorrect because the B-DNA structure is a right-handed double helix, but the Watson-Crick model was not specifically proposed based on this structure.
**Option C:** This option is incorrect because the Z-DNA structure is a left-handed double helix, and while it is an important variant of DNA, it was not the basis for the Watson-Crick model.
**Clinical Pearl / High-Yield Fact**
The Watson-Crick model has been widely accepted as the correct structure of DNA, and it has been supported by numerous experimental evidence. This model has far-reaching implications for our understanding of genetics, molecular biology, and the transmission of genetic information.
**Correct Answer:** C.