Final answer:
Double-stranded DNA breaks are repaired by homologous recombination, a conservative process employing multiple proteins for accurate repair, and non-homologous end joining, an error-prone mechanism that directly ligates broken DNA ends.
Step-by-step explanation:
Double-stranded breaks (DSBs) in DNA can occur due to various reasons such as errors during DNA replication or environmental factors. Two primary pathways repair these breaks: homologous recombination and non-homologous end joining. Homologous recombination is a complex process involving the MRX/MRN complex, Sae2, and Sgs1, among other proteins, which helps accurately repair DNA without causing deletions. This mechanism is often used during meiosis in eukaryotes, playing a crucial role in maintaining genetic diversity. On the other hand, non-homologous end joining is a quicker repair method that does not require a homologous template. Instead, it involves directly ligating the broken ends of the DNA together, which may result in the deletion of some DNA sequences at the break point. This method is error-prone compared to homologous recombination but is a vital mechanism for repairing DSBs when homology is not available. Both pathways are essential to cell survival and exhibit evolutionary conservation due to the imperative of accurate DNA repair to sustain life.