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Learn about horizontal agarose gel electrophoresis, from gel pouring to DNA sample preparation. Discover how electrophoresis works, detect DNA fragments using fluorescent dyes, and understand the Mendelian inheritance pattern of PV92 Alu insertion. Follow a human DNA typing example in a Molecular Biology Lab. Capture the process with a picture!
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Horizontal AgaroseGel Electrophoresis • Pour gel • Sample preparation depends on Application • Electrophoresis (constant voltage) detect with fluorescent dye (eg., ethidium bromide, SYBR, etc)
How It Works • The DNA samples are loaded into wells of an agarose gel and electrophoresed, along with loading dyes. • An electrical field applied across the gel causes the DNA fragments in the samples to move from their origin (a sample well) through the gel matrix toward the positive electrode. Why? • Small DNA fragments migrate faster than larger ones. • The loading dyes are of 2 different sizes, corresponding to very small DNA fragments and very large DNA fragments.
The PV92 Alu insertion is inherited in a simple Mendelian pattern with each parent contributing one "Allele" to the offspring. If an allele for the PV92 Alu insertion is represented by (+) and the absence of the allele is indicated by (-), the three possible genotypes can be expressed as (+/+), (+/-) and (-/-). Their inheritance can be summarized as follows: • (-/-)neither parent contributed Alu insertion • (+/-)received Alu insertion from one parent • (+/+)both parents contributed Alu insertion
ALU Gel Example Human DNA typing by the Molecular Biology Lab: Determination of an ALU insertion polymorphism by PCR
