Final answer:
The enzyme topoisomerase breaks the DNA phosphate backbone during DNA replication, relieving tension and preventing the strand from uncoiling too quickly.
Step-by-step explanation:
The protein responsible for breaking the DNA phosphate backbone and keeping the strand from uncoiling too quickly during DNA replication is topoisomerase. This enzyme works ahead of the replication fork, solving tension problems caused by the winding and unwinding of DNA. Topoisomerase makes a cut in the phosphate backbone, allows the helix to relax, and then reseals the cut. Other proteins involved in DNA replication include helicase, which separates the DNA strands; single-stranded binding proteins, which prevent the strands from reannealing, and primase, which synthesizes an RNA primer for DNA polymerase to begin synthesizing the daughter strand.