Rosalind Franklin and the Discovery of DNA Structure
Introduction
Rosalind Franklin was a brilliant scientist who played a key role in the discovery of the structure of DNA. Her work had a profound impact on our understanding of genetics and biology.
Basic Concepts
DNA (deoxyribonucleic acid) is a molecule that contains the genetic instructions for all living things. It is made up of four different types of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). These nucleotides are arranged in a specific order, which determines the genetic code.
Equipment and Techniques
Rosalind Franklin used a variety of equipment and techniques to study the structure of DNA. These included:
X-ray crystallography:This technique uses X-rays to create a diffraction pattern of a crystal. The diffraction pattern can be used to determine the structure of the crystal. Photo 51: This is a famous X-ray diffraction image of DNA that was taken by Rosalind Franklin. It provided crucial information about the structure of DNA.
Types of Experiments
Rosalind Franklin conducted a series of experiments to study the structure of DNA. These experiments included:
Diffraction experiments:These experiments used X-ray crystallography to create diffraction patterns of DNA crystals. Fiber diffraction experiments: These experiments used X-ray diffraction to create diffraction patterns of DNA fibers.
Data Analysis
Rosalind Franklin's data analysis played a key role in the discovery of the structure of DNA. She was able to use her diffraction patterns to determine the following:
The diameter of the DNA molecule The distance between the nucleotides in the DNA molecule
* The helical arrangement of the nucleotides in the DNA molecule
Applications
Rosalind Franklin's work on DNA structure has had a profound impact on our understanding of genetics and biology. Her discoveries have led to the development of new drugs and treatments for a variety of diseases.
Conclusion
Rosalind Franklin was a brilliant scientist who made a major contribution to the discovery of the structure of DNA. Her work has had a profound impact on our understanding of genetics and biology.
Rosalind Franklin and DNA Structure
Key Points
- Rosalind Franklin was a British chemist and X-ray crystallographer who made significant contributions to the understanding of the structure of DNA.
- In 1952, Franklin took an X-ray diffraction image of DNA known as "Photograph 51", which provided crucial data for the discovery of the double helix structure of DNA.
- James Watson and Francis Crick used Franklin's data without her knowledge or consent to develop their model of DNA, which they published in 1953.
- Franklin's contributions were initially overlooked, but her work has since been recognized as essential to the discovery of the structure of DNA.
Main Concepts
Franklin's X-ray diffraction image showed that DNA had a helical structure and that the bases were stacked perpendicular to the helix axis. This information was crucial for Watson and Crick to develop their model of DNA, which showed that the DNA molecule is a double helix with two strands of nucleotides held together by hydrogen bonds.
Franklin's work helped to revolutionize our understanding of DNA and genetics, and her contributions are now recognized as essential to the field of molecular biology. Her legacy continues to inspire scientists around the world.
Experiment: Verifying the Helical Structure of DNA using X-ray Diffraction
Objective:
To experimentally demonstrate the helical structure of DNA, as discovered by X-ray diffraction experiments conducted by Dr. Rosalinda Franklin.
Materials:
X-ray diffraction apparatus (X-ray source, detector, sample holder) Crystalline DNA solution
Cuvette Camera
Procedure:
1. Prepare the crystalline DNA solution by dissolving high-quality DNA in a buffer solution and allowing it to crystallize.
2. Load the DNA crystals into the X-ray diffraction apparatus.
3. Expose the crystals to X-rays.
4. Measure the scattered X-ray intensity at various angles.
5. Plot the intensity versus the scattering angle to generate an X-ray diffraction pattern.
Key Procedures:
Crystallization of DNA:DNA is crystallized to create a regular arrangement of molecules, which is necessary for X-ray diffraction. X-ray exposure: The DNA crystals are exposed to X-rays, which scatter off the DNA molecules.
Intensity measurement:The intensity of the scattered X-rays is recorded at different angles. Diffraction pattern analysis: The intensity versus scattering angle plot shows a distinct pattern, known as the diffraction pattern, which reveals the structure of the DNA molecule.
Significance:
Rosalind Franklin's X-ray diffraction experiments were crucial in determining the helical structure of DNA, a discovery that earned her Nobel Prize (awarded posthumously). The X-ray diffraction technique allows scientists to investigate the structure of biomolecules such as proteins and nucleic acids by analyzing the scattering pattern of X-rays. This understanding is essential for deciphering the genetic code and advancing fields like genetics, medicine, and biotechnology.
Results:
The X-ray diffraction pattern of DNA crystals exhibits a characteristic X-shaped pattern, consistent with a helical structure. The distance between the layers of the helix and the diameter of the DNA molecule can be calculated from the pattern. These measurements validate the model proposed by Watson and Crick and confirm the helical structure of DNA.