Biotechnology and its two core techniques

From curd to insulin

Think of a spoon of curd put into warm milk at night. In the morning the milk has turned into curd. Tiny bacteria did the work. People have used living cells like this for thousands of years, for curd, bread and wine. This is the old form of biotechnology.

The word is now used for much more. The European Federation of Biotechnology defines it as the use of natural science together with organisms, cells or their parts, to make products and services. NCERT lists examples such as the test tube baby, the making of a gene in the laboratory, a DNA vaccine and the repair of a faulty gene.

Many of these are possible because of one skill: moving a gene from one organism into another. Human insulin made by a bacterium is the best-known example. This chapter shows how that is done.

Two core techniques

NCERT names two techniques that are at the centre of modern biotechnology.

• Genetic engineering. The chemistry of the genetic material, DNA or RNA, is changed. The changed material is then put into a host organism. The host gets a new phenotype, which means a new visible or measurable trait.
• Bioprocess engineering. The surroundings are kept free from germs, so that only the wanted microbe or cell grows. It can then grow in large amounts and make a product such as an antibiotic, a vaccine or an enzyme. This is the part that turns a laboratory result into a medicine in a bottle. NCERT calls these chemical engineering processes, because a large tank is run like a chemical plant.

Why not breed the plants and animals?

For ages, farmers improved their plants and animals by cross-breeding. This is traditional hybridisation. It has a weakness. A cross brings together the whole set of genes of the two parents. The offspring gets the wanted gene, and also many unwanted genes. A breeder has to repeat the cross for generations to remove them.

Genetic engineering is more exact. It lets us isolate one gene or a small set of genes and put it into another organism. The technique is called recombinant DNA technology. A recombinant DNA is a DNA made by joining DNA from two different sources.

The first recombinant DNA

In the early 1970s, Stanley Cohen and Herbert Boyer cut out a piece of DNA that carried a gene for resistance to an antibiotic. They linked it to a plasmid of the bacterium Salmonella typhimurium. A plasmid is a small circle of DNA that lives apart from the main chromosome and copies itself. An enzyme called DNA ligase joined the two. Then the new DNA was put into Escherichia coli. There it copied itself with the host's own DNA polymerase and made many copies. Making many copies of a gene in a host is called cloning of the gene.

The three basic steps

Every genetic modification, from the first to the newest, needs the same three steps.

1. Identify the DNA with the wanted gene.
2. Introduce that DNA into a host.
3. Maintain the introduced DNA in the host, and pass it on to the offspring of the host.

The tool kit

To carry out these steps we need five things. The next lessons take each one.

• Restriction enzymes to cut the DNA.
• Polymerases to copy the DNA.
• Ligases to join the pieces.
• Vectors to carry the gene into the host and make copies of it.
• A host organism in which the work is done.

You should see a straight line. A line on a log scale means that the number multiplies by the same factor in each equal step of time. That is the pattern of doubling. This is the base of the bioprocess: a few cells become billions in a few hours.

Try it in Python

The program counts the cells of a culture after a few doublings.

Practise with new numbers

Common mistakes

• Saying that biotechnology began with genetic engineering. Curd, bread and wine are older biotechnology.
• Mixing up the two core techniques. Genetic engineering changes the genes. Bioprocess engineering keeps the culture clean and grows it in large amounts.
• Thinking that the old way and the new way are the same. Cross-breeding moves whole sets of genes. Recombinant DNA technology moves one chosen gene.
• Forgetting the third step. A gene that is put into a host but is not maintained and passed on is lost.

Remember these

• Genetic engineering alters the genetic material and puts it into a host. Bioprocess engineering keeps the culture sterile and grows it in large amounts.
• The three basic steps: identify the DNA, introduce it into a host, and maintain it in the host and in its offspring.
• The tool kit: restriction enzymes, polymerases, ligases, vectors and a host.
• Cohen and Boyer linked an antibiotic resistance gene to a plasmid of Salmonella typhimurium. The gene was then cloned in Escherichia coli.

Check yourself

Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.

1. Name the two core techniques of modern biotechnology, and say in one line what each does.

2. Why is recombinant DNA technology more exact than cross-breeding?

3. What are the three basic steps of making a genetically modified organism?

4. A culture of 3000 cells per millilitre doubles every 20 minutes. How many cells per millilitre are there after one hour?

5. What is meant by cloning of a gene?

References

• NCERT (2023). Biology, Textbook for Class XII, chapter 9, Biotechnology: Principles and Processes.
• Clark M. A., Douglas M. and Choi J. (2018). Biology 2e, OpenStax, chapter 17.1 (Biotechnology).