Molecular Diagnostics for Infectious Diseases

Deoxyribonucleic Acid (DNA) is a fundamental building block of life. It was first isolated in 1869 by Dr. Johannes Freidrick Miescher of Switzerland, a physician and biologist (Figure 1). Dr. Miescher suspected that it was involved in heredity. James Watson (an American biologist), Francis Crick (an English physicist and biochemist), and Maurice Wilkins (a New Zealand native, physicist, and molecular biologist) were awarded the Nobel Prize in 1962 for the discovery of the three-dimensional double helix structure of DNA. DNA consists of 4 different nucleotides; Adenine, Thymine, Guanine, and Cytosine (also A, T, G, and C, respectively). Nucleotides contain a nitrogenous base, a ribose sugar, and a phosphate. The nucleotides subunits bond to create a linear DNA sequence. When a complementary sequence is present a double stranded spiral structure is formed that is commonly recognized as DNA molecules (Figure 2). These molecules encode the essential blueprint of life forms and the specific sequence is uniquely different between individuals. Some viruses store genetic information as Ribonucleic acid (RNA) instead of DNA. The RNA molecule is similar to DNA except that there is a substitution of the nucleotide base uracil for thymine, the ribose sugar differs, and it is usually single stranded. RNA is read by ribosomes in groups of three nucleotides at a time, called codons, and is translated into proteins. Proteins could be described as microscopic machines that perform the vast majority of chemical reactions and biological functions of cells.