These DNA samples exhibit the nucleosome repeat of 200 base-pairs when electrophoresed on agarose gels. Electrophoreetic analysis of this DNA can be used to illustrate the structure of chromatin. The DNA also provides economical standards for small DNA fragments. The DNA was obtained by digestion of calf thymus nuclei with low (Nucleosome 1), medium (Nucleosome 2), and high (Nucleosome 3) amounts of micrococcal nuclease. The DNA is dissolved in gel-loading buffer and are ready for electrophoresis.