Chemicals

［y-32P］dATP，［α-32P］dATP，and［α-32P］dCTP were purchased from Amersham Corp.，Arlington Heights，I1.Agarose and a nick translation reagent kit were obtained from Bethesda Research Laboratories，Gaithersburg，Md.；Gene Screen membrane and nitrocellulose filters were products of New England Nuclear Corp.，Boston，Mass.Proteinase K was purchased from Boehringer Mannheim Biochemicals，Indianapolis，Ind.DNase I was obtained from Worthington Diagnostics，Freehold，N.J.Macoloid used for purifying DNase I was kindly supplied as a gift by NL Chemicals，Hightstown，N.J.Phenol was obtained from Sigma Co.，St.Louis，Mo.，and redistilled.All other chemicals were reagent grade.(https://www.daowen.com)