DNA: Time Line of the Discovery of the Structure

Time Line of the Discovrey of the Structure of DNA is a long process of discovery that culminated in 1953 with the publication by Watson and Crick of their paper.

Prehistory

It was intuitively obvious that the direct descendants of living organisms, especially the offspring of humans, inherited some of their traits of their parents. The process of reproduction of all animals was obvious. It was understood that large seeds, such as acorns, produced a new generation of plants.

Dawn of civilization

Horticulture, animal husbandry and breeding were practiced.

1600

• 1637: the peak of tulip mania, in the Netherlands in March 1637

1700

• 1710: The German physician and botanist Rudolf Jakob Camerarius is credited with the first empirical demonstration that plants reproduce sexually.
• 1780: Antoine Lavoisier, among others, advanced of the science of modern chemistry (the "chemical revolution") around 1780.

1800

• 1802: John Dalton introduced the modern notion of a simple atomic theory.
• 1859: Charles Darwin published Origin of the Species, proposing that all species are somehow related.
• 1866: Gregor Mendel published the basic principles of genetics (specifically on the distribution of non-blending traits among generations of offspring), but his results are ignored for many years.
• 1869: Friedrich Miescher identified "nuclein", which we know today as deoxyribonucleic acid (DNA). It took 50 years for others to recognized the importance of this work.

1900

• 1900: Mendel's theories are independently rediscovered by Hugo de Vries, Carl Erich Correns and Erich Tschermak von Seysenegg and promoted by William Bateson.
• 1902: Archibald Edward Garrod published The Incidence of Alkaptonuria: A Study in Chemical Individuality, which associates Mendel's theories with this human disease.
• 1928: Frederick Griffith observed that a 'transforming factor' was responsible for changing the properties of bacteria. The experiment consisted of injecting a dead strain of disease-causing bacteria into a mice, along with a live strain that doesn't cause disease. The result was that the live strain became virulent by obtaining some component from the dead strain.
• 1929: Phoebus Levene concluded that DNA is made up of nucleotides which consist of a sugar, phosphate group, and a base.
• 1944: Oswald Avery and others identified DNA in pneumococcus bacteria as the 'transforming principle'.

1950

• 1950: Erwin Chargaff published his two rules:

1. That in any double-stranded DNA, the number of guanine units is equal to the number of cytosine units and the number of adenine units is equal to the number of thymine units.

2. that DNA composition is species-specific.

• 1950: Maurice Wilkins and Raymond Raymond Gosling took the first images of DNA, producing medium-quality pictures of X-ray diffraction in aligned fibres of DNA.
• 1951: James Watson and Francis Crick start to work together at Cavendish Laboratory in Cambridge.
• 1951: Rosalind Franklin hired to improve X-ray crystallography quality at Kings.
• 1951: Watson and crick proposed a 3-helix model of DNA with helices on the inside and base pairs on the outside. It was quickly recognized as erroneous. The King’s group complained that DNA was their domain and Sir Lawrence Bragg instructed Watson and Crick to cease all work on DNA.
• 1952: Franklin determined that there are two forms of the DNA helix which she called A and B.
• November 1951: Watson attended a lecture by Franklin at Kings where she mentions the B form of helix.
• 1952: Alfred Hershey and Martha Chase established that DNA is responsible for heredity by showing that viral DNA initiates the replication of new viruses.
• 1952: Rosalind Franklin produced X-ray diffraction photographs of crystallized DNA fibers at King's College, London.
• May 1952: "Photograph 51" is taken by Rosalind Franklin's PhD student, Raymond Gosling.
• November: 1952: Franklin decided to leave Kings College and announces her decision.
• November: Jerry Donohue suggested to Watson that he try modeling DNA with the enol rather than keto forms of the base pairs. The enol was the correct form.
• December 1952: Max Perutz gave Watson and Crick a Medical Research Council (MRC) report that contained some of Franklin's work including her identification of the unit cell of DNA as belonging to the crystal space group called face-centered monoclinic C2. Crick, with more experience in theoretical crystallography that the helices ran in opposite directions. In the report, Franklin indicated that the phosphates are on the outside and provided measurements of the interphosphate distances. Crick suggest to Watson to try the phosphates on the outside.

1953

• January 5: Linus Pauling proposed a triple stranded Helix structure for DNA. Bragg decided to set Watson and Crick on the problem once more.
• January 20: Wilkins shows Watson "Photo 51".
• February 28: Watson recognized how the hydrogen bonding between the base pairs occur. Watson and Crick walk to The Eagle pub and announce to the patrons that they have found the "secret of life".
• March: Watson and Crick build a proper metal model of DNA and show it to their colleagues.
• April 25: Nature published their Watson and Crick's brief paper. Franklin and Wilkins publish articles in same issues. Franklin's article includes Photo 51.

Afterward

Progress was made over the next decades in understanding the function of DNA.

• 1958: Crick declares the "central dogma of molecular biology".
• 1965: Marshall Nirenberg is the first person to sequence the bases in each codon.
• 1990-2003: the Human Genome Project.
• May 21, 2010, Science journal reported that the Craig Venter had created Mycoplasma laboratorium, a bacteria that used an existing cell of a Mycoplasma capricolum bacterium with its DNA removed and replaced with fully-synthetic DNA molecule generated from a computer file by based on a modified version of the Mycoplasma mycoides genome.
• 2013: CRISPR demonstrates fast, cheap and precise DNA editing.

Further reading

• Robert Olby, Robert, The Path to the Double Helix: The Discovery of DNA, (1974 & revised 1994) ISBN 0-486-68117-3 (2013) ISBN 0486166597