Lambda DNA is digested to completion with the appropriate Fermentas PureExtreme restriction enzyme(s)， purified and dissolved in storage buffer. DNA fragments contain various sticky ends depending on the restriction enzyme used for preparation of the marker. Marker can be labeled radoactively with T4 Polynucleotide Kinase. Alternatively， it can be labeled radioactively or non-radioactively with Klenow Fragment or Klenow Fragment， exo- with the fill-in reaction， protocols.