Introduction

Before working through this chapter, it helps to recall three ideas from earlier study: the structure of DNA, how protein synthesis works, and the basics of genetic engineering. Genetic engineering is the deliberate manipulation of DNA and of natural cellular processes like protein synthesis, and one of its most powerful uses is moving a gene out of one organism and inserting it into the DNA of another -- of the same species or a completely different one. DNA assembled this way is called recombinant DNA (rDNA), and the technique itself is recombinant DNA technology. Both sit within the wider field of biotechnology, which can be defined as applying scientific and engineering principles to biological agents so that they process material into useful goods and services. The word 'biotechnology' itself is much older than the modern gene-based techniques it now describes -- it was already in use before the 20th century for everyday practices like making idli, dosa, dairy products, bread, or wine, even though none of those traditional processes would count as biotechnology in today's sense. This chapter surveys where modern biotechnology is actually applied, starting with medicine, where recombinant DNA technology now makes large-scale production of therapeutic hormones and proteins possible.