 Although the proteins and specific mechanisms involved in their initial phases differ , the two pathways are similar in that they both require single @-@ stranded DNA with a 3 ’ end and the RecA protein for strand invasion . The pathways are also similar in their phases of branch migration , in which the Holliday junction slides in one direction , and resolution , in which the Holliday junctions are cleaved apart by enzymes . The alternative , non @-@ reciprocal type of resolution may also occur by either pathway . 
