A method for the preparation of size marker for synthetic oligonucleotides

Terminal deoxynucleotidyltransferase was used for the addition of [alpha-32P]dCTP to the 3'-OH termini of oligo(dT)12-18. A collection of oligonucleotides with chain lengths ranging continuously from 13-mer to over 100-mer was generated. The reaction mixture was then mixed with oligo(dT)12-18 labeled with [gamma-32P]ATP by T4 polynucleotide kinase. A sequence ladder with the bottom base as 12-mer was then formed. These oligonucleotides served as size marker for the purification and identification of oligonucleotides on polyacrylamide gel.