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DNA gel electrophoresis is usually performed for analytical purposes, often after amplification of DNA via polymerase chain reaction (PCR), but may be used as a preparative technique for other methods such as mass spectrometry, RFLP, PCR, cloning, DNA sequencing, or southern blotting for further characterization.
Electrophoresis techniques used in the assessment of DNA damage include alkaline gel electrophoresis and pulsed field gel electrophoresis. For short DNA segments such as 20 to 60 bp double stranded DNA, running them in polyacrylamide gel (PAGE) will give better resolution (native condition). [ 1 ]
Agarose gel has large pore size and good gel strength, making it suitable as an anticonvection medium for the electrophoresis of DNA and large protein molecules. The pore size of a 1% gel has been estimated from 100 nm to 200–500 nm, [ 4 ] [ 5 ] and its gel strength allows gels as dilute as 0.15% to form a slab for gel electrophoresis. [ 6 ]
The DNA fragments that result are then separated and detected using electrophoresis. There are two common methods of separation and detection, capillary electrophoresis (CE) and gel electrophoresis. Each STR is polymorphic, but the number of alleles is very small. Typically each STR allele will be shared by around 5 - 20% of individuals.
Kenneth and Noreen Murray introduced this technique as Southern. The second innovation is the gel electrophoresis that is based on separation of mixtures of DNA, RNA, or proteins according to molecular size, which was also developed at Johns Hopkins University, by Daniel Nathans and Kathleen Danna in 1971.
Pulsed-field gel electrophoresis (PFGE) is a technique used for the separation of large DNA molecules by applying an electric field that periodically changes direction to a gel matrix. [ 1 ] [ 2 ] Unlike standard agarose gel electrophoresis , which can separate DNA fragments of up to 50 kb, PFGE resolves fragments up to 10 Mb. [ 1 ]
DNA profiling is a forensic technique in criminal investigations, comparing criminal suspects' profiles to DNA evidence so as to assess the likelihood of their involvement in the crime. [ 1 ] [ 2 ] It is also used in paternity testing , [ 3 ] to establish immigration eligibility, [ 4 ] and in genealogical and medical research.
Thus, urea is typically utilized for gel preparation; however, researchers need to be aware that the amount of urea used will affect the overall temperature required to separate the DNA. [6] The gel is loaded, the sample is placed on the gel according to the type of gel that is being run—i.e. parallel or perpendicular—the voltage is ...