DNA polymerase delta synthesizes DNA across a single-stranded gap during mismatch repair (Longley et al. 1997, Zhang et al. 2005, Constantin et al. 2005, reviewed in Prindle and Loeb 2012). RPA stimulates the activity of DNA polymerase delta (Dong et al. 1999). DNA polymerase delta does not displace strands during synthesis (Randahl et al. 1988).