Which option is a correct practical point about handling restriction enzymes?

Correct answer: Keep them cold and protected from heat

The direct answer is option A: restriction enzymes should be kept cold and protected from heat. Restriction enzymes are proteins, and their three-dimensional shape is necessary for recognizing and cutting the correct DNA sequence. Heat can disrupt this shape and reduce or destroy enzyme activity. Therefore laboratories store these enzymes under cold conditions, commonly in a freezer, and avoid repeated warming or unnecessary exposure. Option A is correct because cold handling helps preserve activity. Option B is wrong because boiling generally denatures proteins and would inactivate the enzyme. Option C is wrong because dry soil is not a controlled, sterile storage condition and can damage or contaminate the preparation. Option D is wrong because sunlight and heat can harm the enzyme. The exact storage temperature depends on the manufacturer, so instructions must be followed. Memory cue: enzymes are delicate proteins—keep them cold, clean, and brief outside storage.