text: Although the concept of molecular-weight markers has been retained, techniques of development have varied throughout the years. New inventions of molecular-weight markers are distributed in kits specific to the marker's type.
  An early problem in the development of markers was achieving high resolution throughout the entire length of the marker. Depending on the running conditions of gel electrophoresis, fragments may have been compressed, disrupting clarity. To address this issue, a kit for Southern Blot analysis was developed in 1990, providing the first marker to combine target DNA and probe DNA. This technique took advantage of logarithmic spacing, and could be used to identify target bands ranging over a length of 20,000 nucleotides.