Which enzymes are mainly used for cutting DNA?

Correct answer: Restriction enzymes

The direct answer is A, restriction enzymes. These enzymes are proteins made by many bacteria. They recognize particular short DNA sequences, called recognition sites, and cut the DNA at or near those sites. This is why they are often called molecular scissors. Step by step: first, the enzyme finds its specific DNA sequence; next, it breaks the sugar-phosphate backbone of both DNA strands; finally, the resulting fragments can be joined to another DNA fragment in recombinant DNA work. Option A is correct because restriction enzymes are specifically used for controlled DNA cutting. Option B, lipase, mainly breaks lipids or fats, not DNA. Option C, amylase, digests starch into smaller sugars, so it is not a DNA-cutting enzyme. Option D, cellulase, breaks cellulose, a plant cell-wall carbohydrate, and does not normally cut DNA. Remember: restriction enzyme means a sequence-specific DNA cutter; ligase joins DNA after cutting.