The gaps between segments of DNA on the lagging strand produced by restriction enzymes are rejoined/sealed by
**Core Concept**
The question is testing the student's understanding of DNA replication and repair mechanisms, specifically the process of sealing gaps in the lagging strand produced by restriction enzymes.
**Why the Correct Answer is Right**
During DNA replication, the lagging strand is synthesized discontinuously, resulting in short, staggered fragments called Okazaki fragments. These fragments are separated by gaps, which are sealed by DNA ligase. This enzyme is essential for sealing the gaps between the Okazaki fragments, allowing the lagging strand to be fully replicated. DNA ligase forms a phosphodiester bond between the 3'-end of one nucleotide and the 5'-end of the adjacent nucleotide, effectively sealing the gap.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because DNA polymerase, while involved in DNA replication, is not responsible for sealing gaps between Okazaki fragments.
**Option B:** This option is incorrect because the proofreading and editing functions of DNA polymerase are essential for maintaining DNA fidelity, but it is not involved in sealing gaps.
**Option C:** This option is incorrect because DNA helicase is involved in unwinding the double helix, allowing access to the template strands for replication, but it is not involved in sealing gaps.
**Clinical Pearl / High-Yield Fact**
The process of sealing gaps between Okazaki fragments is crucial for maintaining genomic integrity, as unsealed gaps can lead to mutations and genetic instability.
**Correct Answer:** C. DNA ligase. DNA ligase.