Ciro Santilli Technique widely used to measure the size of DNA strands, most often PCR output of a region of interest.
A simple sample application is gel electrophoresis alelle determination.
In the case of indel mutations (see limits of gel electrophoreses for minimal size difference issues), it is possible to determine the allele with gel electrophoresis. You can just read out the alleles right in the gel. It is a thing of beauty.
As of 2020, this method appears to be much cheaper than DNA sequencing approaches.
- 1982 www.pnas.org/doi/pdf/10.1073/pnas.80.6.1579 DNA fragments differing by single base-pair substitutions are separated in denaturing gradient gels by Fischer and Lerman (1982). It is possible then.
Biologists are obsessed with these!
These can be used to break cells apart from tissue, and also break up larger DNA or RNA molecules into smallers ones, suitable for sequencing.