Deoxyribonucleic acid, generally referred to as DNA by its acronym, is the basis of life, which
contains the information for the development and functioning of all the living organisms.
The DNA research began in 1868, when Swiss physiological chemist Friedrich Miescher first
identified what he called “nuclein” inside the nuclei of human white blood cells. In 1889, R.
Altmann separated nuclein from protein and because of its acidic character he named it nucleic
acid. Phoebus Levene identified the components of DNA and showed that they were linked
in the order phosphate- sugar-base to form units which he referred as nucleotide and
suggested that the DNA molecule consisted of a string of nucleotide units linked together
through the phosphate groups, which is the ‘backbone’ of the molecule. The role of DNA in
heredity was recognized in 1944, when Avery and co-workers published their famous result
that DNA and not proteins were the carriers of genetic information (Avery et al., 1944). The
complementary base-pair rule was found by Chargaff in 1950 (Chargaff et al., 1950). A milestone
in DNA research was the double helix structure which was proposed by Watson and Crick in
1953 based upon the X-ray fiber diffraction data from fibres of DNA obtained by Rosalind
Franklin (Watson and Crick, 1953). From the double helical structure, it was immediately
obvious how information could pass from one generation to the next by synthesis of DNA
complementary strands from parent strands. In 1962 they received the Nobel Prize in Chemistry
for the discovery along with the crystallographer Maurice Wilkins. The first published account
of the directed chemical synthesis of an oligonucleotide occurred in 1955 when Michelson
and Todd reported the preparation of a dithymidinyl nucleotide (Michelson and Todd, 1955).
In the late 1950’s Khorana and his group were able to synthesize oligoribonucleotides that
were used to confirm the Genetic Code. In 1968, Khorana received the Nobel Prize in
Physiology or Medicine for their interpretation of the genetic code and its function in protein
synthesis. Khorana’s method was revolutionary at the time and produced a truly remarkable
feat: the synthesis of an active 72-mer tRNA molecule, which was published in Nature
(Agarwal et al., 1970). However, it was not until the late 1970’s that the development of DNA
research became explosive, when synthetic DNA fragments became commercially available.
Pohl and Jovin first observed the salt-induced cooperative conformational changes of the
synthetic DNA poly(dG-dC).poly(dG-dC) duplex, from a right-handed helix to left handed
helix from the circular dichroism study (Pohl and Jovin, 1972)