The protein that prevents the reannealing of DNA during replication is called Single-stranded Binding Protein (SSB).

Here's how it works:

1. DNA Helicase unwinds the double helix, separating the two strands.

2. SSB proteins bind to the single-stranded DNA to prevent the strands from rejoining. This is essential because the separated strands are highly unstable and could easily reanneal.

3. SSB proteins help maintain the single-stranded conformation until the DNA polymerase can use the single strands as templates for new DNA synthesis.

Without SSB proteins, the DNA strands would rapidly re-associate, making it impossible for the DNA polymerase to replicate the DNA.