Noun
English Wikipedia has an article on:DNA ladderWikipedia
DNA ladder (plural DNA ladders)
(genetics) A reagent consisting of a solution of DNA of specified length; used in gel electrophoresis as a standard.
The size(s) of PCR products is determined by comparison with a DNA ladder (a molecular weight marker), which contains DNA fragments of known size, run on the gel alongside the PCR products (see Fig. 3). Source: Internet
The gel also shows a positive control, and a DNA ladder containing DNA fragments of defined length for sizing the bands in the experimental PCRs. Source: Internet
Nucleic acids main An agarose gel of a PCR product compared to a DNA ladder. Source: Internet