In eukaryotes, two primary models for how homologous recombination repairs double-strand breaks in DNA are the double-strand break repair (DSBR) pathway (sometimes called the "double Holliday junction model") and the synthesis-dependent strand annealing (SDSA) pathway. In the case of double strand breakage, the 3' end is degraded and the longer 5' end invades the contiguous sister chromatid, forming a replication bubble. As this bubble nears the broken DNA, the longer 5' antisense strand again invades the sense strand of this portion of DNA, transcribing a second copy. When replication ends, both tails are reconnected to form two Holliday Junctions, which are then cleaved in a variety of patterns by proteins. An animation of this process can be seen here.