DNA Discovery: Crick and Watson

Francis Crick

• Crick is renowned for his co-discovery of the structure of DNA, a pivotal achievement in scientific history.
• His early career involved studying physics followed by a shift to biology and X-ray diffraction of proteins.
• In 1951, he met James Watson and they began their groundbreaking collaboration on DNA.
• Alongside Watson, Crick unveiled the double helix structure of DNA in 1953, earning them the Nobel Prize in 1962.
• He made notable contributions to the understanding of the genetic code.
• In his later years, he studied developmental neurobiology and human consciousness, becoming a Distinguished Research Professor at the Salk Institute for Biological Studies.

James Watson

• Watson, a prominent geneticist and biophysicist, is known for his co-discovery of the DNA double helix structure.
• He revolutionized biological research and earned a Nobel Prize for his work.
• From 1950 to 1951, he focused on viral research at the University of Chicago.
• In 1951, he joined the Cavendish Laboratory in Cambridge, UK, and began his partnership with Francis Crick.
• Together, they published a landmark paper on DNA structure in 1953.
• He later held a professorship at Harvard University, and in 1989, led the international Human Genome Project.
• His research contributed to understanding the structure and function of DNA, advancing molecular research.

DNA: A Revolutionary Discovery

• Crick and Watson's discovery of DNA's double helix structure in 1953 is considered a landmark achievement in science.
• DNA, or deoxyribonucleic acid, carries genetic information within cells and determines hereditary patterns in living organisms.
• Understanding DNA's structure is vital for comprehending its replication process and gene function.
• The race to discover DNA's structure predates Watson and Crick's work, with Oswald Avery's 1944 discovery establishing that DNA carries genetic information.
• This discovery led to significant advancements in research and medicine, enabling gene sequencing, genetic engineering, and research into inherited medical conditions.

DNA Discovery

• Sydney Brenner was one of the first to see Watson and Crick's DNA model.
• His research focused on developmental and molecular biology, with a focus on organ development, cell apoptosis, and transparent nematodes.
• He worked with Francis Crick to uncover the process of encoding amino acids in proteins.
• Brenner received the Nobel Prize in 2002 for his contributions.

Discovery of DNA Structure

• Knowledge of DNA's structure was essential for advancing heredity studies.
• Scientists in the 1950s, including Linus Pauling, Rosalind Franklin, and Maurice Wilkins, were actively involved in this research.
• While the components of DNA were known, the structure and replication process remained unclear.
• Crick and Watson employed a unique approach: building physical 3D models.
• This strategy, aided by Rosalind Franklin's data, led to the discovery of the DNA structure within just three days.

DNA Structure - A Landmark Discovery

• This quote aptly reflects the significance of the DNA structure's features: "We have discovered the secret of life."
• The image illustrating this section depicts the double helix structure, emphasizing Crick and Watson's co-discovery in 1953.
• The DNA molecule is characterized by a double helix structure resembling a twisted ladder.
• The backbone of the ladder is made up of alternating phosphate and sugar units.
• Base pairs: adenine(A) with thymine(T) and guanine(G) with cytosine(C), form the rung of the ladder, following complementary base pairing.
• The sequence of bases constitutes the genetic code.
• This structure allows for DNA replication: Each half ladder produces a complementary strand, resulting in two identical DNA molecules.
• The discovery of DNA's structure was a major scientific achievement in the 20th century, providing a foundation for groundbreaking advancements in molecular biology and genetics.

Rosalind Franklin

• Rosalind Franklin was a British chemist whose vital contributions to the understanding of DNA's structure were largely overlooked.
• Her expertise in X-ray crystallography enabled her to produce the first clear image of crystalline DNA, revealing its double helix shape.
• Her work played a significant role in the discovery of DNA's structure, yet she was not fully acknowledged for it.
• Franklin's groundbreaking research on the structure of major crop viruses further solidified her scientific prowess.

The Most Beautiful X-ray Photographs

• Franklin's X-ray photograph of DNA, known as Photograph 51, revealed its helical shape, two-stranded structure, and the backbone's position.
• However, the photograph was shared with Watson and Crick without Franklin's knowledge.
• Her contributions were not acknowledged until after her death.
• Her work was pivotal in understanding the structure through X-ray crystallography, paving the way for later research.

Maurice Wilkins

• Maurice Wilkins, a biophysicist, is known for his X-ray studies on DNA, which contributed to understanding its structure.
• He had a collaborative yet challenging relationship with Rosalind Franklin.
• He shared Franklin's Photograph 51 with Watson and Crick without her consent.
• He shared the Nobel Prize in Physiology or Medicine in 1962 with Francis Crick and James Watson but often receives less recognition for his role.

Grant and Bequest

• Rosalind Franklin received a grant to study the polio virus, demonstrating the significance of her research.
• She also made a bequest to support Aaron Klug, signifying her commitment to scientific advancement.

Photograph 51

• Photograph 51 was taken using an X-ray and required 60 hours to produce.

Frederick Sanger: A Biographical Sketch and Scientific Contributions

• Frederick Sanger, a two-time Nobel laureate, was a pioneer in sequencing proteins, RNA, and DNA.
• His method for sequencing DNA molecules revolutionized molecular biology, opening the doors for advancements in medicine, gene therapy, and genetic manipulation.
• He received the Nobel Prize in Chemistry in 1958 and 1980 for his work on insulin and DNA sequencing.
• He established the Wellcome Sanger Institute in Cambridge, UK, to further research in the field of genomics.

Scientific Path

• Sanger's scientific journey was influenced by a strong belief in truth and conscience, which led him to a career in science.
• He dedicated himself to meticulously researching the amino acid sequence of insulin, a groundbreaking achievement.
• His determination and persistence allowed him to decipher the complete amino acid sequence of insulin, proving that each protein has a unique amino acid composition and 3D structure.

Sanger's Sequence Data

• The provided image showcases DNA data and highlights Sanger's work in sequencing.

Sanger's Contributions to DNA Sequencing

• He pioneered the use of radioactive isotopes to label DNA fragments, enabling sequencing.
• His dideoxy chain-termination method, developed in 1977, revolutionized DNA sequencing.
• This method enabled the isolation, cloning, and reattachment of DNA fragments, paving the way for gene therapy and treatment techniques.

Nobel Prizes in Chemistry

• Frederick Sanger is the only person to have won two Nobel Prizes in Chemistry.

Genetic Research

• He won his first Nobel Prize for work related to insulin in 1958.
• He continued to focus on nucleic acids, studying RNA and DNA at the Cambridge Laboratory of Molecular Biology.

Sequencing DNA

• He developed a method using radioactive isotopes to "label" DNA fragments, enabling sequencing.
• He focused on DNA sequencing due to its larger size and double-helix structure.
• In 1977, he pioneered the dideoxy chain-termination method, which uses inhibitors to stop DNA strands from extending during replication.

Sequencing the Human Genome

• He sequenced the DNA of cell mitochondria in 1981.
• His work led to sequencing the entire human genome, encompassing approximately 3 billion base pairs.

Important Collaborators and Other Contributions

• His work was influenced by the collaboration with Francis Crick and James Watson, who discovered the double helix structure of DNA.
• John Sulston, a biologist and Nobel laureate, was a crucial collaborator in genome research.

Summary of Sanger's Legacy

• Frederick Sanger's methods revolutionized DNA sequencing, enabling the mapping of the human genome and driving advancements in biomedical science.