Final answer:
The formation of Holliday junctions, while a step in homologous recombination, is not part of the initial generation of 3'-protruding ends for strand invasion. It occurs subsequent to strand invasion.
Step-by-step explanation:
The process that generates 3'-protruding ends for strand invasion is crucial for homologous recombination, an important aspect of DNA repair and genetic diversity. During this process, several steps occur including DNA resection, where the DNA is trimmed back to produce single-stranded (ssDNA) 3'-overhangs, and RecA-mediated synapsis, where the RecA protein facilitates the pairing of the exposed ssDNA with a homologous sequence.
Moreover, single-strand invasion takes place, where the 3'-ssDNA invades the homologous DNA strand. In contrast, the formation of Holliday junctions is a subsequent step in the recombination process that occurs after strand invasion, to allow crossover and exchange of genetic material, but is not involved in the initial generation of 3'-protruding ends.