D, Models of RMD mediated by SSA (RMD/SSA) or BIR (RMD/BIR). When a DSB is created in the middle of two repeats, the DNA ends of both sides are resected, generating 3' ssDNA overhangs, until the repeat sequences on opposite sides are both exposed. Then ssDNA of the repeat sequences anneal, resulting in a product with internal sequences deleted. When a DSB is generated close to one repeat, ssDNA formed in one repeat first can invade the other repeat still in duplex using BIR, which can also give rise to a deletion product identical to the SSA product after cleavage of D-loop. Pink arrow: putative structure-specific endonucleases to cleave non-homologous tails; blue arrow: putative structure-specific endonucleases to cleave the D-loop. 