Single-strand binding proteins function by...

Single-strand binding proteins function by...

• A. Unwinds the double helix.
• B. Bind to and stabilize single-stranded DNA.
• C. Ligates Okazaki fragments.
• D. Repress transcription at the origin.

Answer: (B)

Single-strand binding proteins stabilize the exposed single-stranded DNA after the double helix is unwound. When helicase opens the replication fork, ssDNA becomes vulnerable to re-annealing and to nucleases. SSBs coat the ssDNA, keeping it extended and accessible for DNA polymerases to copy the template. They also prevent the formation of secondary structures like hairpins that could hinder replication, ensuring smooth, efficient synthesis. In bacteria, this stabilizing role is carried out by the SSB protein, and in eukaryotes a similar function is performed by replication protein A. Unwinding the DNA is the job of helicase, ligating Okazaki fragments is done by DNA ligase, and repressing transcription at the origin is not a function of SSB.

Single-strand binding proteins stabilize the exposed single-stranded DNA after the double helix is unwound. When helicase opens the replication fork, ssDNA becomes vulnerable to re-annealing and to nucleases. SSBs coat the ssDNA, keeping it extended and accessible for DNA polymerases to copy the template. They also prevent the formation of secondary structures like hairpins that could hinder replication, ensuring smooth, efficient synthesis. In bacteria, this stabilizing role is carried out by the SSB protein, and in eukaryotes a similar function is performed by replication protein A. Unwinding the DNA is the job of helicase, ligating Okazaki fragments is done by DNA ligase, and repressing transcription at the origin is not a function of SSB.