Question

Which is the role of restriction enzymes?
to isolate the selected gene
to cut DNA into fragments of different lengths
to move and separate the strands of DNA
to join the sticky ends of DNA fragments

Answer 1

B : to cut DNA into fragments of different lengths
Restriction enzymes cut DNA molecules at specific sequences called restriction sites.

Answer 2

"Helicase" is an enzyme that moves and separate the strands of DNA and "ligase" is an enzyme that joines (ligates) the sticky ends of DNA fragments.