The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication?
(a) Nothing needs to be done because the two strands will be separated after replication is complete.
(b) Topoisomerases break the covalent bonds of the backbone allowing the local unwinding of DNA ahead of the replication fork.
(c) Helicase unwinds the DNA and rewinds it after replication is complete.
(d) DNA repair enzymes remove torsional stress as they replace incorrectly paired bases.
Answer: B