Which factor stabilizes the unwound single strands during replication?

Which factor stabilizes the unwound single strands during replication?

• A. Helicase
• B. Single-strand binding proteins
• C. Topoisomerase
• D. DNA Ligase

Answer: (B)

Stabilizing unwound single-stranded DNA during replication is achieved by single-strand binding proteins. After helicase opens the double helix, exposed single strands tend to reanneal or form secondary structures, which would block replication. Single-strand binding proteins bind tightly to these strands, keeping them stretched out and protected from nucleases, so the DNA polymerases can efficiently copy them. Helicase’s job is to separate the two DNA strands, but it doesn’t keep the single strands from re-forming base pairs on its own. Topoisomerase relieves the twisting (supercoiling) ahead of the fork to prevent tangling, not to stabilize the single strands. DNA ligase seals breaks on the sugar-phosphate backbone during lagging-strand synthesis, which is about connecting fragments, not stabilizing the exposed strands.

Stabilizing unwound single-stranded DNA during replication is achieved by single-strand binding proteins. After helicase opens the double helix, exposed single strands tend to reanneal or form secondary structures, which would block replication. Single-strand binding proteins bind tightly to these strands, keeping them stretched out and protected from nucleases, so the DNA polymerases can efficiently copy them.

Helicase’s job is to separate the two DNA strands, but it doesn’t keep the single strands from re-forming base pairs on its own. Topoisomerase relieves the twisting (supercoiling) ahead of the fork to prevent tangling, not to stabilize the single strands. DNA ligase seals breaks on the sugar-phosphate backbone during lagging-strand synthesis, which is about connecting fragments, not stabilizing the exposed strands.