05/01/13

May 1, 2013 was the last day for my internship regarding capillary electrophoresis. When I got to RPI, my mentor, rather than make another buffer or sample and run it through the capillary electrophoresis machine, she explained to me how to interpret even further graphs like the one attained a week before. As mentioned during my poster presentation (and probably somewhere in my previous blog posts), the DNA sample contains fluorescent markers that allow lasers to detect the DNA fragments. The graph produced at the end of the capillary electrophoresis process displays this test result and aids in interpreting the very fragments. The capillary machine determines the size of the DNA fragments in a sample based on the data detected by the lasers. The computer connected to the machine then depicts the lengths of the myriad of fragments as peaks on the graph. Thus, it helps determine the length of the detected DNA fragments.

The information accumulated all throughout several of these graphs is used to create the DNA profile. "Two points of reference are used to help the software as it determines the lengths: 1) the GeneScan software uses the internal size standard, which contains DNA fragments of known sizes; and 2) the Genotyper software uses allelic ladders as a point of comparison for the designation of the number of repeats in the DNA sample at particular chromosomal locations, since the peaks within the allelic ladder correspond to known fragment lengths at those locations."(An allelic ladder is a standard sample which contains all the alleles for a specific gene so that when it undergoes electrophoresis, there's a clear separation of the different alleles in the form of bands.)

The DNA Examiner works with both softwares and documents what the allele values are at each of the chromosomal locations analyzed and then compiles it to constitute a DNA profile (like the the graph of my previous post).

All in all, even to the very last day, just when I thought I knew all there was to capillary electrophoresis, I realized that my knowledge of it makes up only a parcel in the grand scheme of all things. ;)