What role does the overproduction of organisms play in natural selection?

What is the next step in the process after a substrate enters the active site of an enzyme

The structure of a dna molecule is best described as a. one long strand of nucleic acids b. two strands of dna nucleotides joined by hydrogen bonds c. two strands of amino acids joined by hydrogen bonds d. one long strand of amino acids

Which enzyme is responsible for “unzipping" the dna by breaking the hydrogen bonds between the nucleotides?