Final answer:
The main eukaryotic protein involved in homologous recombination is Rad51.
Step-by-step explanation:
The main eukaryotic protein involved in homologous recombination is Rad51. Rad51 is the homolog of RecA in bacteria and RadA in archaea. It plays a crucial role in repairing double-stranded DNA breaks by facilitating the exchange of genetic information between homologous chromosomes.