A technique called electrophoresis is used to obtain DNA profiles, relying on sections of our DNA that are known as non-coding DNA (DNA that does not code for a protein). Electrophoresis sorts DNA strands according to length. The electrophoresis “gel” acts as a filter that sorts DNA strands.
(1) The gel is created using powdered agarose, buffer, a microwave, a gel mold, and a gel comb to create the wells for the DNA sample. (2) DNA samples are placed into the holes at one end of the gel. (3) The electrical current is connected, with the negative current closest to the wells. The DNA samples are repelled by the negative charge. (4) The short strands move faster through the gel so they will be farther from the start. Strands of the same lengths end up together in groups that are visible to the naked eye. (5) The lengths are measured in bp (base pairs), which is not an exact measurement but accurate enough for the comparisons.
PCR is used to magnify a quantity of DNA in only several hours. (1) Thermocycler separates a strand of DNA from a double helix (works like helicase). Heat breaks the hydrogen bonds between base pairs. (2) The sample is cooled with a solution of free nucleotides, DNA primers, and Taq polymerase, for the primers to bind (anneal) to the end of DNA strands. (3) This makes a complete copy of the templates. Each time PCR is done, the quantity doubles.
A limitation of PCR is that the DNA sample must be pure, otherwise any contamination or abnormalities will also be magnified.
One case study of DNA profiling used for determining paternity was in the situation of Anna Nicole Smith’s daughter, Dannielynn. Danielynn’s paternity was in question ever since her birth in the Bahamas last September. After Anna Nicole Smith’s death in February, the paternity of Dannielynn became all the more important, especially in the case of custody. After a many judges and trials, the testing was granted, and a sample was obtained from Dannielynn. The judge in the Bahamas ruled that the DNA test results confirmed at 99.99% certainty that a previous boyfriend and photojournalist was the father.
