Blocked 5'-termini in the fragments of chromosomal DNA produced in cells exposed to the antitumor drug 4'-[(9-acridinyl)-amino]methanesulphon-m-anisidide (mAMSA).

Comparison of the sensitivity of DNA isolated from untreated and mAMSA-treated PY815 mouse mastocytoma cells to hydrolysis by E.coli 3'-exonuclease III and phage lambda or phage T7 5'-exonucleases show that the fragments of chromosomal DNA produced by mAMSA treatment have free 3'-OH termini and blocked 5'-termini.