Critical thinking : Do magnets need to touch a piece of iron or another magnet to exert a magnetic force on the iron or other magnet?

Restriction enzymes are used in making recombinant dna. describe the role restriction enzymes perform when constructing recombinant dna.

What is the one part of the nucleotide  that differs among the other different nucle  tides?

This is a biological reaction due to a stimulus. i need this quickly !