Problem 108 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

The double helical structure of DNA was proposed by : |KCET 1998] (a) Meicher (b) Watson and Crick (c) Khorana (d) - Emil Fischer

Step-by-Step Solution

Answer

Watson and Crick (b)

Step 1: Understand the Question

The question is asking who proposed the double helical structure of DNA. This is a historical question that relates to the discovery of DNA's structure.

Step 2: Review the Options

The options given are (a) Meicher, (b) Watson and Crick, (c) Khorana, and (d) Emil Fischer. We need to identify which of these individuals or pairs proposed the double helix model.

Step 3: Recall Historical Context

James Watson and Francis Crick are famously known for proposing the double helical structure of DNA. They published their findings in 1953, which was a groundbreaking discovery in the field of molecular biology.

Step 4: Eliminate Incorrect Options

Given the historical context, we can rule out options (a) Meicher, (c) Khorana, and (d) Emil Fischer as not being associated with the proposal of the DNA double helix structure.

Step 5: Select the Correct Answer

Based on our understanding, Watson and Crick (option b) are indeed the individuals behind this scientific proposal. Therefore, option (b) is the correct answer.

Key Concepts

Watson and Crick

In 1953, James Watson and Francis Crick made a groundbreaking discovery in the field of genetics by proposing the structure of DNA as a double helix. Their work was pivotal and earned them the Nobel Prize in Physiology or Medicine in 1962. The journey to discovering this structure was collaborative, involving insights from other scientists such as Rosalind Franklin and Maurice Wilkins.

Here are some key aspects of Watson and Crick's contributions:

• They built a model that suggested DNA is made of two strands forming a helix, resembling a spiraled staircase.
• Their model demonstrated how genetic information could be stored and replicated, explaining the mechanism of heredity which is the basis of genetics.
• Watson and Crick's work was heavily dependent on the X-ray crystallography images produced by Rosalind Franklin, which provided critical evidence for the helical structure.

Despite the controversy over scientific credit, Watson and Crick's model revolutionized biology, giving rise to the field of molecular biology, the discipline that studies the molecular mechanisms of DNA and proteins.

Double Helix

The structure of DNA is famously known as a double helix, a term coined by Watson and Crick. This refers to the shape formed by two intertwined strands of nucleotides. Each nucleotide strand is composed of a sugar-phosphate backbone and nitrogenous bases.

The double helix structure provides stability and flexibility, allowing DNA to encode genetic information. Here’s how this ingenious structure works:

• The sugar-phosphate backbones form the sides of the ladder, with the nitrogen bases as the rungs.
• The bases pair specifically, with adenine pairing with thymine, and guanine with cytosine, which are held together by hydrogen bonds.
• This specific base pairing is critical for DNA replication and the transmission of genetic information.

The double helix model is essential for understanding genetic processes as it illustrates how strands can unwind and duplicate, ensuring genetic continuity across generations.

Molecular Biology

Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field truly began to flourish after the discovery of the DNA double helix by Watson and Crick. With a better understanding of DNA's structure, scientists delved deeper into the processes involving DNA, RNA, and protein synthesis.

Some areas explored in molecular biology include:

• Gene expression and regulation, which involves understanding how genes are turned on and off in cells.
• Replication and repair of DNA, ensuring that genetic information is accurately passed down and maintained.
• The study of RNA, which acts as a messenger between DNA and protein synthesis, known as transcription and translation.

Molecular biology plays a crucial role in modern science, informing research in genetics, biochemistry, and biotechnology. It impacts practical applications like genetic engineering, medical diagnostics, and treatment development.