Biotechnology: Principles and Processes NEET Notes 2027 with PDF

Biotechnology: Principles and Processes is Chapter 9 of NCERT Class 12 Biology and part of Unit 9, Biotechnology and Its Applications, of the NEET UG syllabus. These notes cover genetic engineering, restriction enzymes, gel electrophoresis, cloning vectors and pBR322, competent hosts, the steps of the process, PCR, bioreactors and downstream processing, with a free notes PDF.

Biotechnology: Principles and Processes NEET Notes

Section-wise key points from NCERT Chapter 9, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.

Biotechnology: Principles and Processes at a Glance

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

What is biotechnology and what are its principles?

Biotechnology uses live organisms or enzymes from organisms to make products and processes useful to humans. Today the term mostly means processes that use genetically modified organisms on a large scale.

• Curd, bread and wine making are microbe-mediated processes, so they can also be seen as a form of biotechnology. In vitro fertilisation, gene synthesis, DNA vaccines and correcting a defective gene are also part of it.
• European Federation of Biotechnology (EFB) definition: ‘The integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services’.
• Two core techniques gave birth to modern biotechnology: genetic engineering and bioprocess engineering.
• Traditional hybridisation often carries undesirable genes along with the desired ones. Genetic engineering (recombinant DNA, gene cloning, gene transfer) introduces only the desirable genes.
• An alien piece of DNA multiplies in a host only if it is linked to an origin of replication, the sequence that starts replication. Making many identical copies of a template DNA is called cloning.

The First Recombinant DNA

• Stanley Cohen and Herbert Boyer made it in 1972 by linking an antibiotic resistance gene with a native plasmid of Salmonella typhimurium.
• The gene was cut out with restriction enzymes (‘molecular scissors’) and joined to the plasmid vector with DNA ligase.
• The recombinant DNA was transferred into Escherichia coli, where it replicated using the host’s DNA polymerase. This was called cloning of the antibiotic resistance gene in E. coli.
• Three basic steps in genetically modifying an organism: (i) identify DNA with desirable genes; (ii) introduce it into the host; (iii) maintain it in the host and transfer it to the progeny.

Restriction Enzymes: the Molecular Scissors

The key tools of recombinant DNA technology are restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. Restriction enzymes cut DNA at specific recognition sequences.

• In 1963 two enzymes that restrict the growth of bacteriophage in E. coli were isolated. One added methyl groups to DNA; the other cut DNA and was called restriction endonuclease.
• Hind II, the first restriction endonuclease that depended on a specific sequence, was isolated five years later. It cuts at a recognition sequence of six base pairs.
• More than 900 restriction enzymes are known, isolated from over 230 strains of bacteria.
• Naming: first letter from the genus, next two letters from the species, then the strain, then a Roman number for the order of isolation. In EcoRI (Escherichia coli RY 13), ‘R’ comes from the strain name.
• Each restriction endonuclease recognises a specific palindromic sequence, which reads the same on both strands when read in the same orientation, for example 5′ GAATTC 3′ and 3′ CTTAAG 5′.
• They cut a little away from the centre of the palindrome, between the same two bases on opposite strands, leaving overhanging single-stranded sticky ends. Sticky ends form hydrogen bonds with complementary ends, which helps DNA ligase join them.
• The vector and the source DNA must be cut with the same restriction enzyme to make a recombinant vector molecule.

How does gel electrophoresis separate DNA fragments?

Gel electrophoresis separates DNA fragments by size: negatively charged DNA moves towards the anode through an agarose gel, and smaller fragments move farther.

• The most common matrix is agarose, a natural polymer extracted from seaweeds. It separates fragments by a sieving effect.
• DNA is seen only after staining with ethidium bromide and exposure to UV light, as bright orange bands. Pure DNA cannot be seen in visible light without staining.
• The separated bands are cut out of the gel and extracted. This step is called elution, and the purified fragments are joined to cloning vectors.
• Agarose gel electrophoresis is also used to check how far a restriction digestion has progressed.

Cloning Vectors: Features and pBR322

Plasmids and bacteriophages replicate inside bacteria independently of chromosomal DNA, so an alien DNA linked to them multiplies to their copy number.

• Bacteriophages have very high copy numbers per cell. Some plasmids have only one or two copies per cell, others 15 to 100 or more.
• Modern vectors are engineered for easy linking of foreign DNA and easy selection of recombinants from non-recombinants.

pBR322 and Insertional Inactivation

• pBR322 is an E. coli cloning vector with restriction sites (Hind III, EcoR I, BamH I, Sal I, Pvu II, Pst I, Cla I), ori, and the antibiotic resistance genes ampR and tetR. rop codes for proteins involved in plasmid replication.
• Foreign DNA ligated at the BamH I site of the tetracycline resistance gene makes recombinants lose tetracycline resistance.
• Agrobacterium tumifaciens, a pathogen of several dicot plants, delivers T-DNA that turns normal plant cells into a tumour. Its Ti plasmid is now modified into a non-pathogenic cloning vector.

Selection by antibiotic inactivation is cumbersome because it needs plating on two plates with different antibiotics, so colour-based selection was developed.

How is recombinant DNA put into a host cell?

DNA is hydrophilic and cannot pass through cell membranes, so bacterial cells are first made competent to take it up.

• Cells are treated with a specific concentration of a divalent cation such as calcium, which increases DNA entry through pores in the cell wall.
• The cells are incubated with recombinant DNA on ice, given a brief heat shock at 42 °C, and put back on ice.
• If the recombinant DNA carries an ampicillin resistance gene, only transformants grow on ampicillin plates; the ampicillin resistance gene is the selectable marker.

Processes of Recombinant DNA Technology

Recombinant DNA technology follows a fixed sequence of steps, from isolating DNA to marketing the product.

• 1. Isolation of DNA
• 2. Fragmentation of DNA by restriction endonucleases
• 3. Isolation of the desired DNA fragment
• 4. Ligation of the fragment into a vector
• 5. Transfer of the recombinant DNA into the host
• 6. Culturing the host cells in a medium at large scale
• 7. Extraction of the desired product

Isolation of the Genetic Material

Purified DNA precipitates out after adding chilled ethanol and is seen as fine threads, which can be removed by spooling.

Cutting and Joining DNA

Purified DNA is incubated with a restriction enzyme at the optimal conditions for that enzyme, and the same is done with the vector DNA. The cut gene of interest and the cut vector are mixed and ligase is added to make recombinant DNA.

Polymerase Chain Reaction (PCR)

• PCR makes multiple copies of the gene of interest in vitro using two sets of primers (small, chemically synthesised oligonucleotides complementary to the DNA) and DNA polymerase.
• Each cycle has three steps: denaturation, primer annealing and extension of primers.
• Repeated many times, the segment is amplified about a billion times.
• This needs a thermostable DNA polymerase, isolated from the bacterium Thermus aquaticus, which stays active during high-temperature denaturation.

Obtaining the Foreign Gene Product

• A protein-encoding gene expressed in a heterologous host gives a recombinant protein.
• In a continuous culture system, used medium is drained from one side and fresh medium added from the other, keeping cells in their most active log (exponential) phase for higher yields.
• Bioreactors process large volumes (100 to 1000 litres) and provide optimum temperature, pH, substrate, salts, vitamins and oxygen.
• Stirred-tank bioreactors are the most common: cylindrical or with a curved base, with an agitator, oxygen delivery, foam control, temperature control, pH control and sampling ports. In a sparged stirred-tank reactor, sterile air bubbles are sparged through it.

Downstream Processing

After the biosynthetic stage, separation and purification (together called downstream processing) prepare the product. It is then formulated with preservatives, drugs go through clinical trials, and every product needs strict quality control testing.

Most-asked Facts for NEET: Biotechnology: Principles and Processes

Revise these one-line facts from the NCERT chapter just before the exam.

• Core techniques of modern biotechnology: genetic engineering and bioprocess engineering.
• First recombinant DNA: Stanley Cohen and Herbert Boyer, 1972, plasmid of Salmonella typhimurium.
• First sequence-specific restriction endonuclease: Hind II, with a six base pair recognition sequence.
• EcoRI comes from Escherichia coli RY 13.
• Restriction enzymes recognise palindromic sequences such as GAATTC and leave sticky ends.
• DNA ligase joins the cut ends of DNA.
• In gel electrophoresis DNA moves towards the anode; smaller fragments move farther.
• Agarose comes from seaweeds; DNA bands are seen with ethidium bromide under UV light.
• Extracting separated DNA bands from the gel is called elution.
• pBR322 carries ampR and tetR; insertion at BamH I inactivates tetracycline resistance.
• Blue colonies with a chromogenic substrate mean no insert; colourless colonies are recombinants.
• Ti plasmid of Agrobacterium tumifaciens is used as a plant vector; disarmed retroviruses as animal vectors.
• Competent cells: calcium treatment, then ice, heat shock at 42 °C, and ice again.
• Lysozyme for bacteria, cellulase for plant cells, chitinase for fungi.
• Purified DNA precipitates with chilled ethanol.
• PCR steps: denaturation, primer annealing, extension; thermostable polymerase from Thermus aquaticus.
• Bioreactors handle 100 to 1000 litres; stirred-tank type is the most common.
• Separation and purification after biosynthesis are called downstream processing.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Saying DNA moves towards the cathode. DNA is negatively charged and moves towards the anode.
• Thinking larger fragments travel farther in the gel. The smaller the fragment, the farther it moves.
• Calling blue colonies recombinant. Blue means the plasmid has no insert; recombinants give colourless colonies.
• Saying recombinants in pBR322 (insert at BamH I) grow on tetracycline. They grow on ampicillin but not on tetracycline.
• Writing that restriction enzymes cut exactly at the centre of the palindrome. They cut a little away from the centre, between the same two bases on opposite strands.
• Reading the ‘R’ in EcoRI as ‘restriction’. It comes from the strain, RY 13.
• Naming EcoRI as the first restriction endonuclease. NCERT names Hind II.
• Mixing up exonucleases (remove nucleotides from the ends) and endonucleases (cut within the DNA).
• Thinking DNA is visible in plain light after electrophoresis. It needs ethidium bromide staining and UV light.
• Cutting the vector and source DNA with different restriction enzymes. Both must be cut with the same enzyme to get matching sticky ends.

Biotechnology: Principles and Processes Notes PDF and Related Pages

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• Full topic list: NEET syllabus
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• Source text: NCERT Chapter 9 (NCERT, Class 12 Biology)

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