HISTORY OF DNA RESEARCH

The discovery that DNA was the carrier of genetic information was a process that required many earlier discoveries. The existence of DNA was discovered in the mid 19th century. However, it was only in the early 20th century that researchers began suggesting that it might store genetic information.

Friedrich Miescher (1844-1895) discovered a substance he called "nuclein" in 1869. Somewhat later, he isolated a pure sample of the material now known as DNA from the sperm of salmon, and in 1889 his pupil, Richard Altmann, named it "nucleic acid". This substance was found to exist only in the chromosomes.

In 1929 Phoebus Levene at the Rockefeller Institute identified the components that make up a DNA Molecule. Those components are:

1. The four bases
   1. Adenine (A)
   2. Cytosine (C)
   3. Guanine (G)
   4. Thymine (T)
2. Sugar
3. Phosphate

He showed that the components of DNA were linked in the order phosphate-sugar-base. He called each of these units a nucleotide and suggested the DNA molecule consisted of a string of nucleotide units linked together through the phosphate groups, which are the 'backbone' of the molecule. However Levene thought the chain was short and that the bases repeated in the same fixed order. Torbjorn Caspersson and Einar Hammersten showed that DNA was a polymer.

This was only accepted after the structure of DNA was elucidated by James D. Watson and Francis Crick in their 1953 Nature publication. Watson and Crick proposed the central dogma of molecular biology in 1957, describing the process whereby proteins are produced from nucleic DNA. In 1962 Watson, Crick, and Maurice Wilkins jointly received the Nobel Prize for their determination of the structure of DNA. The Nobel Prize would not have been given to them if it hadn't been for Rosalind Franklin and her famous photograph, Photo Fifty-One. Franklin, however, did not get much attention until recently, because before the Nobel Prize was given to Watson, Crick, and Wilkins, Franklin died of ovarian cancer. The most probable reason Franklin contracted cancer was her exposure to radiation from X-ray diffraction which is what she had used to take the photograph, photo Fifty-one.

DNA profiling was developed in 1984 by English geneticist Alec Jeffreys of the University of Leicester, and was first used to convict Colin Pitchfork in 1988 in the Enderby murders case in Leicestershire, England. This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers). This method is one of the most reliable techniques for identifying a criminal, but is not always perfect, for example if no DNA can be retrieved, or if the scene is contaminated with the DNA of several possible suspects.