When can star activity increase?

Correct answer: In wrong buffer excess enzyme or long incubation

The direct answer is A: star activity can increase in the wrong buffer, with excess enzyme, or after excessively long incubation. A restriction enzyme normally recognizes a particular DNA sequence and cuts there. Under unsuitable conditions, its recognition becomes less strict, so it may cut at similar but non-target sites. Step by step: first, the enzyme is mixed with DNA and buffer; second, the buffer controls salt, pH, and other conditions; third, too much enzyme or too much time increases opportunities for incorrect cutting; therefore extra, unwanted bands may appear. A is correct because it lists known causes. B is wrong because perfect recommended conditions usually reduce star activity, not always increase it. C is wrong because without enzyme no enzyme-mediated star cutting can occur. D is wrong because without DNA there is no substrate to cut. Memory cue: “wrong conditions make relaxed cutting.” Follow the protocol, use the correct buffer and enzyme amount, and avoid unnecessary over-incubation.