Biotechnology: Principles and Processes Class 12 Biology Chapter Notes

Core Principles of Biotechnology

Biotechnology, as defined by the European Federation of Biotechnology (EFB), is the integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services. Modern biotechnology is based on two core techniques:

1. Genetic Engineering: This is the technique of altering the chemistry of genetic material (DNA and RNA). It involves creating recombinant DNA (rDNA), using gene cloning and gene transfer to introduce this altered DNA into a host organism. This process changes the host's phenotype. For example, introducing a gene for insulin production into a bacterium allows the bacterium to produce human insulin.

1. Bioprocess Engineering: This principle involves maintaining a sterile (contamination-free) environment in chemical engineering processes. This is crucial for growing only the desired microbe or eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc. Without sterile conditions, unwanted microbes would grow, contaminating the final product and reducing the yield. Large vessels called bioreactors are used for this purpose.

Key Terminologies

Plasmid

Autonomously replicating circular extra-chromosomal DNA found in bacteria, used as a cloning vector.

Restriction Enzyme

An enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. Also called 'molecular scissors'.

DNA Ligase

An enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. It acts as 'molecular glue'.

Cloning Vector

A small piece of DNA, taken from a virus, a plasmid, or the cell of a higher organism, that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for cloning purposes.

Recombinant DNA (rDNA)

A DNA molecule formed by combining genetic material from multiple sources. It is created by joining a gene of interest to a vector.

Selectable Marker

A gene introduced into a cell that confers a trait suitable for artificial selection, helping to identify transformants. E.g., antibiotic resistance genes.

Bioreactor

A large vessel in which raw materials are biologically converted into specific products by microbes, plant/animal cells, or their enzymes under optimal conditions.

PCR (Polymerase Chain Reaction)

A technique used to amplify a specific DNA segment in vitro, creating millions of copies from a small initial amount.

Downstream Processing

The series of steps including separation and purification of a product after the biosynthetic stage in a bioreactor.

Must Remember for Exams

• The first recombinant DNA was constructed in 1972 by Stanley Cohen and Herbert Boyer by linking an antibiotic resistance gene to a native plasmid of Salmonella typhimurium.
• Restriction enzymes are a part of a bacterium's defense mechanism called the restriction-modification system. They recognize specific palindromic sequences (reading the same on two strands when orientation is kept the same, e.g., 5'-GAATTC-3' for EcoRI).
• Key features required in a cloning vector are: (i) Origin of Replication (ori), (ii) Selectable Marker, (iii) Cloning Sites (Recognition Sites).
• Insertional Inactivation is a method for screening recombinants. If a foreign gene is inserted into the coding sequence of an enzyme (e.g., β-galactosidase), the enzyme is inactivated. Recombinants will not produce the enzyme, leading to a visible change (e.g., white colonies instead of blue).
• Taq polymerase, isolated from the bacterium Thermus aquaticus, is used in PCR because it is a thermostable enzyme that remains active at the high temperatures required for DNA denaturation.
• Not all restriction enzymes create sticky ends; some, like SmaI, create blunt ends by cutting at the same point on both strands.
• For a foreign gene to be expressed in a host, it must be part of an Expression Vector, which contains a promoter and other regulatory sequences recognized by the host's machinery.
• pBR322 is a widely used artificial plasmid vector. It has two antibiotic resistance genes (ampicillin and tetracycline) as selectable markers and several unique restriction sites.
• Agrobacterium tumefaciens, a plant pathogen, is used as a natural genetic engineer to deliver genes into plants. Its Ti plasmid is modified into a cloning vector.

Steps in Recombinant DNA Technology

1. Step 1: Isolation of Genetic Material (DNA) —
2. Step 2: Cutting DNA at Specific Locations —
3. Step 3: Amplification of Gene of Interest (Using PCR) —
4. Step 4: Ligation of DNA Fragment into a Vector —
5. Step 5: Insertion of Recombinant DNA into Host —
6. Step 6: Culturing Host Cells on a Large Scale —
7. Step 7: Extraction and Downstream Processing —

Stirred-Tank Bioreactor vs. Sparged Stirred-Tank Bioreactor

Board Exam Traps and Tips

Diagrams are your best friend in this chapter. A well-labeled diagram of pBR322 (showing ori, rop, antibiotic resistance genes ampR and tetR, and key restriction sites like EcoRI, BamHI) or the steps of PCR (Denaturation, Annealing, Extension with temperatures) can fetch full marks. When explaining insertional inactivation, always specify which colony is recombinant (white) and which is non-recombinant (blue) and why. Also, don't confuse the function of DNA Ligase (joins fragments) with DNA Polymerase (synthesizes DNA). Pay attention to the enzyme names used for cell wall digestion in the DNA isolation step.

Quick Check

• What are the two core techniques that enabled the birth of modern biotechnology? Genetic engineering (recombinant DNA technology) and bioprocess engineering (maintenance of sterile conditions).
• What is a palindromic sequence in the context of restriction enzymes? A DNA sequence that reads the same on the two strands when read in the same orientation (e.g., 5' to 3'). Example: 5'-GAATTC-3' for EcoRI.
• Why is Agrobacterium tumefaciens called a 'natural genetic engineer'? Because it has a natural ability to transfer a piece of its DNA, known as T-DNA (from its Ti plasmid), into the genome of the plants it infects.
• What is the role of 'rop' in the pBR322 vector? The 'rop' gene codes for proteins involved in the replication of the plasmid, helping to control the copy number.

Frequently Asked Questions

Frequently Asked Questions