The essentials
The European Federation of Biotechnology defines biotechnology as the integration of natural science and organisms, cells, parts thereof and molecular analogues for products and services. Modern biotechnology rests on two core techniques:
- Genetic engineering: techniques to alter the chemistry of the genetic material (DNA or RNA), introduce it into host organisms and thus change the phenotype of the host.
- Bioprocess engineering: maintaining a sterile (microbial-contamination-free) environment in chemical engineering processes so that only the desired microbe or eukaryotic cell grows in large quantities to make products such as antibiotics, vaccines and enzymes.
Traditional hybridisation in plants and animals often brings along undesirable genes together with the desired ones. Genetic engineering avoids this by isolating and introducing only the desired genes into the target organism.
A piece of foreign DNA introduced into an organism usually cannot multiply on its own. It must become part of a chromosome or another DNA that has a sequence called the origin of replication (ori), where replication starts. Such a self-replicating unit is called a replicon. When an alien DNA is linked to the ori, it can multiply in the host; this is called cloning.
The first recombinant DNA was made by Stanley Cohen and Herbert Boyer in 1972. They cut a piece of DNA carrying an antibiotic-resistance gene from a plasmid of Salmonella typhimurium and linked it to a plasmid vector. The joining was done with DNA ligase, and the recombinant plasmid was transferred into Escherichia coli, where it replicated.
Key points
- Three basic steps of genetic modification: identify DNA with desirable genes, introduce it into a host, and maintain it in the host and transfer it to progeny.
- Plasmids are autonomously replicating, circular, extra-chromosomal DNA found in bacteria.
- "Molecular scissors" = restriction enzymes; "molecular glue" = DNA ligase.
Common mistakes
- Bioprocess engineering is about large-scale sterile culture, not about cutting DNA.
- Foreign DNA does not multiply just by entering a cell; it needs an ori.