Practice question

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-recommended buffers, minimal enzyme volume, and controlled incubation suppresses star behavior.