1.1 Classical and molecular biotechnology #
1.1.1 Using an organism before anyone could rewrite a gene #
Biotechnology is the deliberate use of a living organism, or of a part of one, to make a product or run a process. Bread, beer, wine, cheese, vinegar, and microbial sewage treatment are biotechnology, and so is keeping the mould or yeast that made the best batch. Any genetic change is whichever mutation or cross happened to be present. The sequence need not be known.
That practice is still production. Industrial strains were improved for decades by mutagenesis and screening before anyone could write a pathway on purpose. Microbiology owns the physiology of those fermentations. These notes own the decision to use it as manufacture and, later, to alter a specified gene. Crop and livestock breeding is the same logic: a phenotype is chosen, and unmeasured alleles travel with it.
1.1.2 What changed in 1973 #
Molecular biotechnology here means that DNA from different sources can be joined and returned to a cell as a replicating molecule. In 1972 Berg’s group joined DNA of the animal tumour virus SV40 to a bacteriophage lambda derivative, and did not put that molecule into Escherichia coli. E. coli lives in the human gut, and a gut bacterium carrying tumour-virus genes was an unknown risk.
In 1973 Cohen, Chang, Boyer, and Helling showed that plasmid DNA cut with EcoRI could be rejoined, transformed into E. coli, and recovered as a molecule that replicated and expressed a resistance the host plasmid had not carried. Cut, join, transform, select became a general method. A specified fragment could sit on a circle with a known origin and a known marker. That is the break with selection. Recombinant human insulin, the commercial landmark, is Chapter 7. The safety argument started at once.
1.2 A defined change, and the discussion that started with it #
The study of A defined change, and the discussion that started with it provides fundamental principles governing cellular architecture, molecular interactions, and physiological regulation.
Genome Editing With The Crispr Cas9 Method, Schematic
1.2.1 What genetic engineering adds #
A selected variant passed a test. You may not know which bases differ, or which differences cause the phenotype. Sequencing can list them afterwards. It does not make the method one that specified them.
Genetic engineering specifies the change: a named insertion, codon, deletion, or pathway. The rest of the genome is supposed to stay put. Off-target cuts, random insertion, and compensatory mutations mean the organism must be checked. Legibility is what makes both use and regulation possible. Engineering does not abolish selection. Directed evolution is selection inside a gene you chose, and factories stack a hardened chassis with a defined insertion.
1.2.2 Asilomar, briefly and accurately #
In July 1974 Berg and colleagues asked scientists to defer two classes of experiment: plasmids carrying new antibiotic-resistance or toxin genes, and animal-virus DNA joined to vectors that replicate in bacteria. The letter was a voluntary moratorium, not a statute, and not a claim that every recombinant molecule was dangerous.
Asilomar, in February 1975, considered lifting that pause. The summary by Berg, Baltimore, Brenner, Roblin, and Singer did not call recombinant DNA safe. It matched experiments to containment. Physical containment is the laboratory’s barriers. Biological containment is a host and vector unlikely to thrive outside. Some experiments were still deferred. The 1976 NIH guidelines turned this into a funding condition in the United States; other countries wrote their own rules.
Asilomar was not a ban and not a regulator. It hardly discussed crops meant to live outdoors, or human germline alteration. It was a meeting of the scientists who wanted to do the work, which is why it could act quickly and why it was an incomplete institution. The surviving principle is Chapter 10’s: do not treat “we can build it” as a risk assessment.
1.3 Key terms, summary, and self-check #
Key terms. Classical biotechnology; molecular biotechnology; selected variant; defined DNA change; recombinant DNA; Cohen–Boyer experiment; Berg letter; moratorium; Asilomar conference; physical containment; biological containment.
Summary. Classical biotechnology selects a product without specifying the genotype. Berg’s group joined viral and phage DNA in 1972 and withheld it from E. coli; the 1973 Cohen–Boyer experiment showed a recombinant plasmid replicating and expressing a new resistance. Genetic engineering specifies the change and therefore has to check it. Asilomar replaced a short moratorium with graded physical and biological containment, and left environmental release, germline alteration, and independent oversight unsettled.
Self-check.
1. What did the 1973 plasmid experiment show that a penicillin fermentation does not?
2. Why did Berg’s group not introduce the SV40–lambda molecule into E. coli?
3. Which two classes of experiment did the 1974 letter ask scientists to defer?
4. What two kinds of containment did Asilomar match to conjectured risk?
5. Name two problems Asilomar did not settle.
