5'->3' double-stranded DNA exonuclease which may also contain a cryptic 3'->5' double-stranded DNA exonuclease activity. Also exhibits endonuclease activity against 5'-overhanging flap structures similar to those generated by displacement synthesis when DNA polymerase encounters the 5'-end of a downstream Okazaki fragment. Required for DNA mismatch repair (MMR) (By similarity). Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding. Specifically expressed in the female germline. Maternally expressed. Accumulates in the developing oocyte. Belongs to the XPG/RAD2 endonuclease family. EXO1 subfamily.