Principles of Genetics and Breeding

1.2.1 Genes

The studies that have revealed the chemistry of genes began in Germany in 1869 when Johann Friedrich Miescher isolated nuclei from pus cells (white blood cells) in waste surgical bandages.

• He found that these nuclei contained a novel phosphorus bearing substance that he named nuclein.
• Nuclein is mostly chromatin, a complex of deoxyribonucleic acid (DNA) and chromosomal protein (Chromatin = DNA +Protein).
• By the end of the nineteenth century both DNA and ribonucleic acid(RNA) had been separated from the protein.

By the beginning of 1930s, P. Levene, W.Jacobs, and others had demonstrated that RNA is composed of a sugar (ribose)plus four nitrogenous bases, and that DNA contains a different sugar(deoxyribose) plus four bases.

They discovered that each base is coupled with a sugar-phosphate to form a nucleotide.