Editing Molecular biology (section)

===Allele-specific oligonucleotide===
{{Main|Allele-specific oligonucleotide}}
Allele-specific oligonucleotide (ASO) is a technique that allows detection of single base mutations without the need for PCR or gel electrophoresis. Short (20–25 nucleotides in length), labeled probes are exposed to the non-fragmented target DNA, hybridization occurs with high specificity due to the short length of the probes and even a single base change will hinder hybridization. The target DNA is then washed and the unhybridized probes are removed. The target DNA is then analyzed for the presence of the probe via radioactivity or fluorescence. In this experiment, as in most molecular biology techniques, a control must be used to ensure successful experimentation.<ref>{{cite book|editor-first2= David Y.|editor-last2=Zhang|editor-last1= Cheng|editor-first1=Liang | name-list-style = vanc |title=Molecular genetic pathology|date=2008|publisher=Humana|location=Totowa, NJ|isbn=978-1-59745-405-6|page=96|url=https://books.google.com/books?id=F_7QXO0ZBigC&q=Allele-specific+oligonucleotide&pg=PA97|access-date=31 December 2016|language=en}}</ref><ref>{{cite book|last1=Leonard|first1=Debra G.B. | name-list-style = vanc |title=Molecular Pathology in Clinical Practice|date=2016|publisher=Springer|isbn=978-3-319-19674-9|page=31|url=https://books.google.com/books?id=cDWFCwAAQBAJ&q=Allele-specific+oligonucleotide&pg=PA30|access-date=31 December 2016|language=en}}</ref>

In molecular biology, procedures and technologies are continually being developed and older technologies abandoned. For example, before the advent of DNA [[gel electrophoresis]] ([[agarose gel electrophoresis|agarose]] or [[SDS-PAGE|polyacrylamide]]), the size of DNA molecules was typically determined by rate [[sedimentation]] in [[sucrose gradient centrifugation|sucrose gradients]], a slow and labor-intensive technique requiring expensive instrumentation; prior to sucrose gradients, [[viscometry]] was used. Aside from their historical interest, it is often worth knowing about older technology, as it is occasionally useful to solve another new problem for which the newer technique is inappropriate.<ref>{{cite book | veditors = Tian J |title=Molecular Imaging: Fundamentals and Applications|url=https://books.google.com/books?id=cBXIBAAAQBAJ&pg=PA550|date=2013|publisher=Springer-Verlag Berlin & Heidelberg GmbH & Co.K |pages=550, 552|access-date=2019-07-08|isbn=9783642343032 }}</ref>