Slt 371 Dna Fingerprinting And Forensic Analysis Laboratory Manual.

The electrophoretic resolution of DNA is carried out on a gel matrix of agarose or polyacrylamide. Agarose is used for horizontal electrophoretic procedure while polyacrylamide gel is used in vertical procedures. Agarose gels are used and cast by boiling agarose in a suitable dilute buffer, pouring into a mould and then allow it to solidify to form a matrix. The porosity of the formed matrix decreases with an increase in agarose concentration. When the DNA samples are loaded in an applied electric field in a gel, DNA molecules migrate toward positively charged electrode at rates determined by their molecular size and conformation. Smaller DNA molecules move faster than larger and bulkier ones.

The DNA resolved on an electrophoresed gel may be stained by planar aromatic compounds like ethidium bromide proflavine and acridine orange. These dyes bond to double stranded DNA by intercalating with base pairs. They have an intrinsic property of fluorescing under UV light. As little as 50ng of DNA may be detected in a gel by staining it with ethidium bromide.