Source: /cirosantilli/gel-electrophoresis-separation-of-snps
= Gel electrophoresis separation of SNPs
* 1982 https://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.