Ch 11 covers the principles and tools of modern biotechnology — genetic engineering (recombinant DNA technology), restriction enzymes, vectors, PCR, gel electrophoresis, and the steps of creating recombinant organisms.
Restriction enzymes: cut DNA at specific palindromic sequences (e.g., EcoRI: 5'-GAATTC-3'), produce sticky or blunt ends. DNA ligase joins fragments. Vectors: carry foreign DNA into host — must have ori, selectable marker (antibiotic resistance), and cloning sites. Common vectors: pBR322 (plasmid), λ phage, BACs, YACs. Gel electrophoresis: separates DNA fragments by size (smaller = faster).
Steps: (1) Isolate gene of interest, (2) Cut with restriction enzyme + cut vector with same enzyme, (3) Ligate (join) to create recombinant DNA, (4) Transfer into host (transformation — CaCl₂/heat shock, microinjection, gene gun/biolistics), (5) Select transformants (antibiotic resistance, blue-white screening), (6) Scale up in bioreactor. PCR (Polymerase Chain Reaction): amplify DNA — denaturation (94°C) → annealing (primer binding) → extension (72°C, Taq polymerase). Exponential amplification.
Download: https://ncert.nic.in/textbook/pdf/lebo111.pdf | Complete book: https://ncert.nic.in/textbook/pdf/lebo1ps.zip
Taq polymerase is a thermostable DNA polymerase isolated from the thermophilic bacterium Thermus aquaticus. PCR involves repeated heating to 94°C (denaturation step), which would destroy normal enzymes. Taq polymerase remains active at high temperatures, so it doesn't need to be added fresh each cycle. Its optimal activity is at 72°C (extension temperature).
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