Wednesday, April 15, 2015

Old School DNA Sequencing: Sanger Method


Before modern technology was available, DNA sequencing was much more tedious and difficult. In the 1950's Dr. Frederick Sanger determined the sequence of amino acids in protein.  This led to the understanding that DNA sequencing was collinear to the sequencing of amino acids. In the 1970's, Dr. Sanger developed a method to determine the exact sequence of nucleotides in a given gene. This method involved placing the DNA sample in  gel that was charred both negatively and positively. The longer strands of DNA would be pulled through the gel slower than the shorter strands, and the DNA separated into bands. The band positions were then "read" in order to determine DNA sequence. To stimulate this, we were given a lab packet in which DNA from four different subjects were tested. We were asked to read each sequence, compare them, and finally determine which subjects carried a disease. Pictures from the lab are posted below. 



In the step above, we determined the sequencing of each subject's DNA by evaluating the bands. This data was then placed in the chart pictured in the last image. 



After comparing the data, it became clear that "Norm" was the only healthy patient. All other subjects showed some disturbance in their DNA that caused them to be effected by the disease. Carol experienced a front shift mutation, Bob experienced a truncation mutation shift, and Abby experienced point mutation. This disease would be unrecognizable were it not for the Sanger Method.

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