DNA: History, Discovery, Structure, Replication, and Application

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Gregor Mendel (1822-1884) often called the "Father of Genetics" was the first person who started research on DNA. Although he was a priest at the Roman Catholic Church but in his free time he would grow pea plants and breeding them in the monastery garden and would analyze the offspring of the mating. Pea plant served as a good model for genetics related experiments since pea plants had different phenotypic traits, which could be visualized by eyes, and one could analyze the genetic results emerging from a cross. The following traits where analyzed by Mendel:
seed texture (round vs wrinkled)
seed color (green vs yellow)
flower color (white vs purple)
growth habit (tall vs dwarf)

Mendel spent almost 8 years growing and mating thousands of pea plants. He kept detailed record of his crosses. His experiments form the very basis of genetic study and inheritance even today.

The very first DNA was isolated from the sperm of salmon in the year 1869 by Friedrich Miescher (1844-1895) who named it "Nuclein". This name was later changed to "nucleic acid" by his student Richard Altmann in the year 1889. Nucleic acid was only found to be associated with chromosomes.

In the year 1928 Frederick Griffith discovered the concept that DNA molecule is inherited from one generation to the next. In his famous experiment with mouse and pneumonia strain he showed how DNA material can be transferred from one generation to the next. Briefly he injected a mouse with a virulent strain of Pneumonia and another with a non-virulent strain. The mouse with the virulent strain died. His next heat killed the virulent strain and injected it inside a mouse. The mouse survived. Next he injected a heat killed virulent strain and a non-virulent strain inside a mouse. Surprisingly the mouse died. He postulated that the virulent killed strain had a genetic material, which was transferred to the non-virulent strain. This process of transfer he called "Transformation".

Oswald Avery discovered the very basis of the inheritance. He carried out Griffith's experiment. He observed when he destroyed carbohydrates, proteins, lipids and ribonucleic acid of pneumonia the injected mouse with the bacterial strain still died but when he destroyed selectively the deoxyribonucleic acid, ...