Introduction to Biotechnology
The term “ biotechnology” was coined by a Hungarian engineer Karl Ereky, in 1919, to refer to the science and methods that permit products to be produced from raw materials with the aid of living organisms. Biotechnology is a diverse field which involves either working with living cells or using molecules derived from them for applications oriented toward human welfare using varied types of tools and technologies. It is an amalgamation of biological science with engineering whereby living organisms or cells or parts are used for production of products and services. The main subfields of biotechnology are medical (red) biotechnology, agricultural (green) biotechnology, industrial (white) biotechnology, marine (blue) biotechnology, food biotechnology, and environmental biotechnology (Fig. 1.1.). In this chapter the readers will understand the potential applications of biotechnology in several fields like production of medicines; diagnostics; therapeutics like monoclonal antibodies, stem cells, and gene therapy; agricultural biotechnology; pollution control ( bioremediation); industrial and marine biotechnology; and biomaterials, as well as the ethical and safety issues associated with some of the products.
The biotechnology came into being centuries ago when plants and animals began to be selectively bred and microorganisms were used to make beer, wine, cheese, and bread. However, the field gradually evolved, and presently it is the use or manipulation of living organisms to produce beneficiary substances which may have medical, agricultural, and/or industrial utilization. Conventional biotechnology is referred to as the technique that makes use of living organism for specific purposes as bread/cheese making, whereas modern biotechnology deals with the technique that makes use of cellular molecules like DNA, monoclonal antibodies, biologics, etc. Before we go into technical advances of DNA and thus recombinant DNA technology, let us have the basic understanding about DNA and its function.
The foundation of biotechnology was laid down after the discovery of structure of DNA in the early 1950s. The hereditary material is deoxyribonucleic acid (DNA) which contains all the information that dictates each and every step of an individual’s life. The DNA consists of deoxyribose sugar, phosphate, and four nitrogenous bases (adenine, guanine, cytosine, and thymine). The base and sugar collectively form nucleoside, while base, sugar, and phosphate form nucleotide (Fig. 1.2). These are arranged in particular orientation on DNA called order or sequence and contain information to express them in the form of protein. DNA has double helical structure, with two strands being complimentary and antiparallel to each other, in which A on one strand base pairs with T and G base pairs with C with two and three bonds, respectively. DNA is the long but compact molecule which is nicely packaged in our nucleus. The DNA is capable of making more copies like itself with the information present in it, as order or sequence of bases. This is called DNA replication. When the cell divides into two, the DNA also replicates and divides equally into two. The process of DNA replication is shown in Fig. 1.3, highlighting important steps.
The double helical structure of DNA where both strands are running in opposite direction. Elongation of the chain occurs due to formation of phosphodiester bond between phosphate at 5′ and hydroxyl group of sugar at 3′ of the adjacent sugar of the nucleotide in 5–3′ direction. The sugar is attached to the base. Bases are of four kinds: adenine (A), guanine (G) (purines), thymine (T), and cytosine (C) (pyrimidines). Adenine base pairs with two hydrogen bonds with thymine on the opposite antiparallel strand and guanine base pairs with three hydrogen bonds with cytosine present on the opposite antiparallel strand
The process of DNA replication. The DNA is densely packed and packaged in the chromosomes. The process requires the action of several factors and enzymes. DNA helicase unwinds the double helix. Topoisomerase relaxes DNA from its super coiled nature. Single-strand binding proteins bind to single-stranded open DNA and prevent its reannealing and maintains strand separation. DNA polymerase is an enzyme which builds a new complimentary DNA strand and has proofreading activity. DNA clamp is a protein which prevents dissociation of DNA polymerase. Primase provides a short RNA sequence for DNA polymerase to begin synthesis. DNA ligase reanneals and joins the Okazaki fragments of the lagging strand. DNA duplication follows semiconservative replication, where each strand serves as template which leads to the production of two complimentary strands. In the newly formed DNA, one strand is old and the other one is new (semiconservative replication). DNA polymerase can extend existing short DNA or RNA strand which is paired to template strand and is called primer.