Watson and Crick are associated with
**Core Concept**
The underlying concept being tested is the discovery of the **structure of DNA**. James Watson and Francis Crick are renowned for their work on the molecular structure of **deoxyribonucleic acid (DNA)**. Their model, known as the double helix, revolutionized the field of molecular biology.
**Why the Correct Answer is Right**
Watson and Crick's discovery of the DNA double helix model explained how genetic information is stored and replicated. They proposed that DNA is composed of two complementary strands of nucleotides, with **adenine (A)** pairing with **thymine (T)** and **guanine (G)** pairing with **cytosine (C)**. This model was a major breakthrough in understanding the **molecular basis of genetics**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while important, it is not the correct association with Watson and Crick.
**Option B:** Incorrect as it does not relate to the discovery of the DNA structure.
**Option C:** Incorrect because it is not the specific contribution of Watson and Crick.
**Clinical Pearl / High-Yield Fact**
The discovery of the DNA structure by Watson and Crick has had a profound impact on **genetics** and **molecular biology**, leading to major advances in fields such as genetic engineering and **personalized medicine**.
**Correct Answer:** D. Structure of DNA