Final answer:
RecA-mediated synapsis facilitates DNA repair and homologous recombination by forming a nucleoprotein filament that invades a homologous DNA molecule, enabling an accurate repair and continuation of DNA replication.
Step-by-step explanation:
During the RecA-mediated synapsis stage in strand exchange, a sophisticated mechanism occurs for DNA repair and homologous recombination, essential for maintaining genetic integrity and diversity. In this process, RecA protein monomers bind to the single-stranded DNA, which results from the trimming activity of 5'-3' exonucleases at the site of a DNA lesion, and form a nucleoprotein filament.
The filament, with its bound 3' end, then searches for and invades a homologous double-stranded DNA molecule, initiating a strand exchange. As a result, replication of the leading strand can continue from the 3' end of the invading strand, accurately repairing the original DNA damage without introducing insertions or deletions.
This RecA-mediated DNA repair process is evolutionarily conserved across species, highlighting its critical role in the survival of species. Moreover, this process also acts during meiosis in eukaryotes, wherein the homolog Rad51 in humans facilitates synapsis and crossing over, allowing for genetic recombination and diversity.