CBSE Class 12 Biology – Biotechnology: Principles and Processes

NCERT-aligned chapter resource | Biology Code 044

1. What is Biotechnology?

Modern biotechnology uses genetic engineering together with bioprocess engineering to obtain useful products or organisms. Recombinant DNA technology is central to the chapter.

2. Tools of Recombinant DNA Technology

Important tools include restriction enzymes, DNA ligase, vectors and competent host cells. Restriction endonucleases recognise specific sequences and cut DNA, while ligase joins DNA fragments.

3. Restriction Enzymes

Many restriction enzymes recognise palindromic DNA sequences and generate defined fragments. Sticky ends can facilitate complementary base pairing between vector and insert.

4. Cloning Vectors

A useful vector contains features that allow replication and selection, such as an origin of replication and selectable marker. Plasmids are common vectors.

5. Polymerase Chain Reaction

PCR amplifies a selected DNA region through repeated cycles of denaturation, primer annealing and extension using a thermostable DNA polymerase.

6. Gel Electrophoresis

DNA fragments can be separated according to size through agarose gel electrophoresis. Smaller fragments generally migrate farther through the gel matrix.

7. Transformation and Selection

Recombinant DNA is introduced into suitable host cells. Selection markers help identify cells that have acquired the vector or desired construct.

8. Bioreactors and Downstream Processing

Bioreactors maintain controlled conditions for large-scale biological production. Downstream processing includes recovery, purification and formulation of the product.

Worked PCR Concept

Each PCR cycle theoretically doubles the target DNA amount. Starting with N copies, ideal amplification after n cycles is approximately N×2ⁿ, ignoring real-world limitations.

Chapter-Specific MCQs

1. DNA fragments are joined by: (A) DNA ligase (B) amylase (C) pepsin (D) insulin. Answer: A.
2. PCR requires repeated: (A) denaturation, annealing and extension (B) translation only (C) meiosis only (D) digestion only. Answer: A.
3. Smaller DNA fragments generally migrate farther in agarose gel because they move more easily through the matrix. Answer: True.

Competency Questions

1. Arrange the major steps of recombinant DNA technology in the correct order.
2. Explain why sticky ends help DNA fragments join.
3. Calculate theoretical PCR amplification after a specified number of cycles.