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#star activity

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RDT Basics

Star activity in restriction enzymes is induced by:

Star activity describes loss of cleavage fidelity where restriction enzymes cut at sequences related but nonidentical to canonical recognition sites. This relaxed specificity is induced by non-optimal conditions including excessive glycerol concentration above five percent introduced from enzyme stocks, high enzyme-to-DNA ratios above ten units per microgram, elevated pH exceeding 8.0, low ionic strength, presence of organic solvents, and prolonged incubation. Under these circumstances, water activity decreases and enzyme conformation alters, reducing discrimination. Using manufacturer-recomme

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Restriction Enzyme and Vector

Star activity in restriction enzymes is caused by:

Star activity refers to loss of specificity where a restriction enzyme cleaves at secondary sequences resembling its canonical site under non-optimal conditions. Fidelity depends on ionic strength, pH, cofactors and glycerol concentration. Elevated glycerol above 5%, high pH above 8.0, low ionic strength, prolonged incubation and high enzyme to DNA ratio relax sequence discrimination. High glycerol and alkaline pH alter enzyme conformation and water activity in the catalytic pocket, permitting cleavage at N* non-canonical positions. Preventing star activity requires using recommended buffer, l

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details