What can happen to a restriction enzyme if temperature becomes too high?

Correct answer: Enzyme can denature or become inactive

The direct answer is option A: excessive temperature can denature a restriction enzyme or make it inactive. Restriction enzymes are proteins, and their activity depends on their three-dimensional shape. At the recommended temperature, the active site usually has the correct shape to recognize a DNA sequence and cut it. Too much heat can disturb protein bonds and unfold the enzyme. Once the active site is damaged, the enzyme may no longer bind or cut DNA efficiently. Option A is correct. Option B is wrong because heating a restriction reaction does not automatically amplify DNA; amplification needs a suitable method such as PCR, primers, nucleotides, and cycling conditions. Option C is wrong because buffer remains a solution of salts and other components; it does not turn into DNA. Option D is wrong because a high temperature does not always dissolve an agarose gel, and gel melting depends on the material and conditions, not on enzyme activity. Follow the enzyme supplier’s recommended temperature and time. Memory cue: heat can unfold proteins, so excess heat can stop enzyme action.