The process of restoring DNA after damage. Genomes are subject to damage by chemical and physical agents in the environment (e.g. UV and ionizing radiations, chemical mutagens, fungal and bacterial toxins, etc.) and by free radicals or alkylating agents endogenously generated in metabolism. DNA is also damaged because of errors during its replication. A variety of different DNA repair pathways have been reported that include direct reversal, base excision repair, nucleotide excision repair, photoreactivation, bypass, double-strand break repair pathway, and mismatch repair pathway.

The repair of a double-strand break in DNA in which the two broken ends are rejoined with little or no sequence complementarity. Information at the DNA ends may be lost due to the modification of broken DNA ends. This term covers instances of separate pathways, called classical (or canonical) and alternative nonhomologous end joining (C-NHEJ and A-NHEJ). These in turn may further branch into sub-pathways, but evidence is still unclear.

Any process that activates or increases the frequency, rate or extent of endodeoxyribonuclease activity, the hydrolysis of ester linkages within deoxyribonucleic acid by creating internal breaks.

The process in which interchain hydrogen bonds between two strands of DNA are broken or 'melted', generating a region of unpaired single strands.

Any process that stops, prevents, or reduces the frequency, rate or extent of DNA recombination.

The disaggregation of a DNA recombinase complex into its constituent strand exchange proteins (recombinases).

The disaggregation of a DNA recombinase complex into its constituent strand exchange proteins (recombinases).

Any process that stops, prevents, or reduces the frequency, rate or extent of double-strand break repair via homologous recombination.

A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent.