Final answer:
Non-homologous end joining (NHEJ) is an error-prone repair mechanism that joins broken DNA ends, while homology-directed repair (HDR) uses a template for accurate repair.
Step-by-step explanation:
The difference between non-homologous end joining (NHEJ) and homology-directed repair (HDR) lies in the mechanism and accuracy of the repair process.
NHEJ is an error-prone repair mechanism that joins the broken DNA ends together without requiring a template. It can result in the loss or addition of nucleotides, leading to potential mutations.
HDR, on the other hand, uses a template, usually a sister chromatid, to accurately repair the broken DNA. It involves a more complex process and is typically error-free.