During DNA replication, what stabilizes the unwound single-stranded DNA to prevent it from reannealing or forming secondary structures?

• A. DNA ligase stabilizes single-stranded DNA by sealing hydrogen bonds between complementary bases
• B. Single-strand binding proteins (SSBs) bind to single-stranded DNA and stabilize it
• C. DNA polymerase stabilizes the replication fork by breaking hydrogen bonds and unwinding the helix
• D. Primase stabilizes single-stranded DNA by adding nucleotides to complete the lagging strand

Answer: (B)

Verified step by step guidance

1. Understand the context of DNA replication, where the double helix is unwound to expose single-stranded DNA (ssDNA) templates for copying.
2. Recognize that single-stranded DNA is unstable and prone to reannealing (reforming the double helix) or forming secondary structures like hairpins, which can interfere with replication.
3. Identify the role of proteins that bind to ssDNA to stabilize it during replication, preventing these unwanted interactions.
4. Recall that Single-Strand Binding proteins (SSBs) specifically bind to ssDNA, coating it and keeping it in an extended, stable form without allowing base pairing.
5. Distinguish SSBs from other enzymes like DNA ligase (which seals nicks), DNA polymerase (which synthesizes new DNA), and primase (which synthesizes RNA primers), none of which stabilize ssDNA by binding to it.