The enzyme used to “flush” the sticky ends of DNA is
**Core Concept**
The question is testing the understanding of DNA repair mechanisms, specifically the process of removing mismatched or damaged bases from the 3' end of a DNA strand. This process is crucial for maintaining genome stability and preventing mutations.
**Why the Correct Answer is Right**
The enzyme responsible for this process is DNA Polymerase 1 (Pol 1), which possesses a 5' to 3' exonuclease activity. This activity enables Pol 1 to remove the sticky ends of DNA, which are the overhanging bases at the 3' end of a DNA strand. This is essential for DNA replication and repair, as it prevents the accumulation of errors and ensures the fidelity of the genetic material.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a DNA repair enzyme. While DNA Polymerase 1 is involved in DNA replication and repair, it is not the primary enzyme responsible for "flushing" the sticky ends of DNA.
**Option B:** This option is incorrect because it is a DNA ligase, which seals the gaps between Okazaki fragments during DNA replication, but it does not remove sticky ends.
**Option C:** This option is incorrect because it is a DNA helicase, which unwinds double-stranded DNA, but it does not remove sticky ends.
**Clinical Pearl / High-Yield Fact**
Remember that DNA Polymerase 1's 5' to 3' exonuclease activity is essential for removing mismatched or damaged bases from the 3' end of a DNA strand, and this process is critical for maintaining genome stability.
**Correct Answer:** Pol 1. DNA Polymerase 1.