The 250 bp DNA Ladder is suitable for sizing double-stranded DNA from 250 bp to 3.5 kb. Prepared from a plasmid containing repeats of a 250-bp DNA fragment, the ladder consists of 14 blunt fragments ranging in length from 250 to 3,500 bp at 250-bp increments. For easy reference on agarose gels, the 1,000 bp band is two- to three-times brighter than the other bands in the ladder. This ladder can be stained with ethidium bromide or radiolabeled using T4 polynucleotide kinase or T4 DNA polymerase.