From Gene to Product: Quick Revision

A brief note on From Gene to Product. Read it before a test. Try each question at the end before you open its answer.

Expression and growth

• Recombinant protein: the protein of a gene that is expressed in a heterologous host, a host of another species.
• Scale: a flask in the laboratory, a bioreactor for large amounts.
• Batch culture: lag, log (exponential), stationary and decline phases.

Bioreactors

• Purpose: to give the optimum temperature, pH, substrate, salts, vitamins and oxygen. NCERT mentions 100 to 1000 litres.
• Stirred-tank: a cylinder or a curved base, with a stirrer that mixes evenly and makes oxygen available.
• Sparged stirred-tank: sterile air is bubbled through as well.
• Parts: agitator, oxygen delivery, foam control, temperature control, pH control and sampling ports.

Downstream processing

• Steps: separation, purification, formulation with preservatives, quality control. A drug also goes through clinical trials.
• Yield: the overall yield is the product of the yields of the steps.

The order of the whole technology

• Isolate the DNA, cut it, separate and elute the fragment, amplify by PCR, ligate into a vector, put into a host, select, grow in a bioreactor, process the product.

Practice with new numbers

A program to try

The program lists the steps of the technology in order.

Mistakes to avoid

• Averaging the yields. The shares multiply.
• Forgetting that the air of a sparged reactor is sterile.
• Saying that a sparged reactor has no stirrer. It has one.
• Leaving out the clinical trials of a drug.

Check yourself

1. Which phase of a batch culture has a steady doubling?

2. What does it mean to sparge a culture?

3. Two steps keep 50 per cent and 40 per cent. What is left at the end?

4. Which comes first, selection of the recombinants or growth in a bioreactor?

Sources

• NCERT (2023). Biology, Textbook for Class XII, chapter 9.
• Clark M. A., Douglas M. and Choi J. (2018). Biology 2e, OpenStax, chapter 17.