Maharashtra State Board · Class 12 · Biology · Chapter 12

Biotechnology — Formula Sheet

Board Formulas

10 formulas

1.Steps of rDNA Technology★
$1) Isolation \to 2) Cutting \to 3) Amplification/Ligation \to 4) Transformation \to 5) Selection$
Five sequential steps. Balbharati asks each with a specific example.
2.Restriction Endonuclease Cutting★
$EcoRI: 5’-GAATTC-3’ \to 5’-G + AATTC-3’; makes sticky ends$
Palindromic recognition site (6 bp). Sticky ends allow ligation of two DNAs cut with same enzyme.
3.Vector Requirements
$ori, selectable marker, cloning sites, small size$
pBR322 has ori, ampR, tetR, and multiple cloning sites.
4.PCR Amplification Cycle★
$Denaturation (94°C) \to Annealing (55°C) \to Extension (72°C)$
One cycle doubles DNA (2ⁿ amplification after n cycles). Uses Taq polymerase.
5.PCR Amplification Formula
$N = N_{0} \times 2^{n}$
n = number of cycles. Starting from 1 molecule, after 30 cycles ≈ 10⁹ molecules.
6.Bt Toxin Gene★
$cry1Ac gene from Bacillus thuringiensis \to Bt cotton (bollworm resistance)$
Cry protein activated in alkaline gut of insect. Non-toxic to mammals.
7.Golden Rice
$psy gene (daffodil) + crtI (bacteria) \to β-carotene in endosperm$
β-carotene is a precursor of vitamin A. Combats vitamin A deficiency.
8.Recombinant Insulin★
$Human insulin gene \to E . co l i \to humulin$
First rDNA therapeutic (Eli Lilly, 1982). Chains A and B produced separately and joined.
9.Transgenic Animals
$Rosie (transgenic cow) — produces human α-lactalbumin in milk$
First transgenic mammal producing human protein in milk.
10.Gel Electrophoresis
$DNA fragments separated by size in agarose gel under electric field$
Smaller fragments move faster. Visualised with ethidium bromide under UV light.