Chapter 9 — Biotechnology: Principles and Processes

Chapter 9 of the Class 12 Biology NCERT textbook, "Biotechnology: Principles and Processes", covers recombinant DNA technology — how restriction enzymes, cloning vectors, and bioreactors are used to produce useful proteins and genetically modified organisms.

• Tools of genetic engineering — Recombinant DNA work depends on a toolkit: restriction enzymes cut DNA at specific sequences, DNA ligase joins fragments, and cloning vectors like plasmids carry foreign DNA into host cells so it can replicate.
• The birth of rDNA technology — Cohen and Boyer's construction of the first recombinant DNA in 1972 established genetic engineering, showing how a gene can be linked to a vector and introduced into a host to create a new genetic combination.
• Amplifying and moving DNA — PCR uses a heat-stable polymerase to multiply a target segment into billions of copies, while DNA is delivered into cells by methods such as calcium-ion heat shock, microinjection, the gene gun, or disarmed pathogens.
• Scaling up with bioreactors — Bioprocess engineering uses bioreactors that control temperature, pH, oxygen, and nutrients to grow cultures and produce recombinant proteins in bulk, bridging laboratory technique and industrial manufacture.

1. 01Restriction endonucleases cut DNA at specific palindromic recognition sequences, producing sticky ends that facilitate joining of DNA fragments using DNA ligase
2. 02Stanley Cohen and Herbert Boyer constructed the first recombinant DNA in 1972 by linking an antibiotic resistance gene with a Salmonella typhimurium plasmid
3. 03Cloning vectors must have an origin of replication (ori), a selectable marker, and suitable cloning sites to allow foreign DNA to replicate in host cells
4. 04PCR (Polymerase Chain Reaction) uses thermostable DNA polymerase from Thermus aquaticus to amplify a target DNA segment up to approximately one billion copies
5. 05DNA can be introduced into host cells by chemical treatment with calcium ions (heat shock method), micro-injection, biolistics (gene gun), or disarmed pathogen vectors
6. 06Bioreactors (100–1000 litre capacity) provide optimal temperature, pH, oxygen, and nutrient conditions for large-scale production of recombinant proteins