Biotechnology and Genetic Modification Notes

Bacteria divide by binary fission about every 20 minutes in good conditions, so modified bacteria quickly reach huge numbers. They can be engineered to make proteins such as insulin and growth hormone. They are not sentient, and their plasmids are easy to isolate, modify and return.

A vector carries DNA into a cell. Restriction enzymes cut the plasmid at a specific sequence and ligase joins in the new gene, making a recombinant plasmid that copies itself with each cell division. Antibiotic resistance genes act as a selectable marker: only bacteria that took up the plasmid survive on antibiotic medium.

With a generation time of about 20 minutes, one cell gives billions of cells in a few hours, so protein can be made on an industrial scale cheaply. Binary fission is asexual, so every daughter cell is genetically identical and inherits the modification. A change that works in one generation works in all later ones.

Bacteria are single-celled prokaryotes with no nervous system, so they cannot suffer. Public objections and regulatory hurdles are fewer, and modified bacteria are easily contained in a bioreactor. Modifying animals raises welfare concerns, and modifying humans raises safety and consent issues.

Bacteria have ribosomes, tRNA and amino acids, so they can translate foreign genes into working proteins. The genetic code is universal. Once the gene is in a plasmid, bacteria make the protein in every generation, with a consistent, pure product.