Biology · Ch 9 — Biotechnology: Principles and Processes
Principles of Biotechnology
Principles of Biotechnology
Among the many techniques involved, two core ones made modern biotechnology possible:
- Genetic engineering — techniques for directly altering the chemistry of genetic material (DNA and RNA), introducing that altered material into a host organism, and thereby changing the host's phenotype.
- Bioprocess engineering — maintaining sterile, contamination-free conditions in chemical-engineering processes, so that only the desired microbe or eukaryotic cell grows at scale, for producing things like antibiotics, vaccines, and enzymes.
A bit of history — Herbert Boyer. Herbert Boyer (b. 1936), while studying E. coli restriction enzymes at UC San Francisco in the late 1960s, found that these enzymes cut DNA in a way that left 'sticky ends' — ideal for precisely pasting DNA fragments back together. Around the same time, Stanley Cohen at Stanford had worked out how to remove plasmids (small circular DNA rings) from bacterial cells and reinsert them into others. Combining Boyer's DNA-cutting/splicing with Cohen's plasmid-reinsertion method let them recombine DNA segments freely and insert them into bacterial cells — turning those cells into manufacturing plants for a chosen protein. This collaboration founded the discipline of biotechnology.
To see why genetic engineering was needed at all, it helps to think about sexual reproduction. Sexual reproduction creates variation by generating new combinations of genes — which is exactly what conventional breeding in plants and animals relies on. But traditional hybridisation has a real limitation: along with the desirable genes you're selecting for, undesirable genes usually get dragged along too. Genetic engineering — through recombinant DNA, gene cloning, and gene transfer — sidesteps this problem entirely, letting scientists isolate and introduce just one desired gene (or a small set of them) without bringing along anything unwanted.
But what actually happens to a piece of DNA introduced into a foreign organism? On its own, it's very unlikely to survive being copied into the organism's progeny. For it to persist, it needs to become part of a chromosome — specifically, a chromosome carrying a sequence called the origin of replication, which is what triggers DNA replication in the first place. Once the alien DNA is linked to an origin of replication, it can replicate and multiply along with the host's own DNA — which is exactly what cloning, or making multiple identical copies of a piece of DNA, means. …