Question

1. helicase separates and unwinds the dna strands from each other. why is an enzyme not required to bring the strands back together (re - anneal them)?

Explanation:

DNA strands have complementary base - pairing. Adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). The hydrogen bonds that form between the complementary bases are sufficient to bring the strands back together under appropriate conditions like correct temperature, salt concentration etc. without the need for an enzyme to specifically drive the re - annealing process.

Answer:

The complementary base - pairing and the resulting hydrogen bonds between bases are enough to re - anneal the DNA strands without the need for an enzyme.