To confirm that the RAD9A is necessary to invoke G2 cell cycle arrest, they tested a double mutant of RAD9A with DNA repair deficient-strain rad52 and found that the cell failed to arrest in G2, further proving that a functional Rad9 gene is needed to induce G2 arrest.
To confirm this they tested a double mutant of rad9 with DNA repair deficient-strain rad52 and found that the cell failed to arrest in G2 further proving that a functioning Rad9 gene is needed to induce G2 arrest. From this they suspected that Rad9 is necessary to invoke G2 cell cycle arrest. 
