Which event marks the beginning of dna replication?
a) formation of replication bubble
b) unwinding of dna helix
c) formation of replication fork

B is the correct answer. The beginning of DNA replication occurs with the unwinding of the DNA helix by a special enzyme. The two strands that form the helix then create a replication fork. The two strands are then oriented differently, one becoming the 'leading strand' and one the 'lagging strand'.