The ABI Prism Genetic Analyzer was one of the first in a lon

The \"ABI Prism Genetic Analyzer\" was one of the first in a long series of pieces of equipment that has replaced gel electrophoresis for analyzing DNA fragments in Forensics. Describe how this piece of equipment works and how it is different from gel electrophoresis. (This is the piece of equipment that generates the \"peaks\" in analysis of the 13 CODIS loci). True or False: PCR is so sensitive that as little as 1 picogram of DNA will give equal results to 2 nanograms or higher of DNA as template. Explain using CODIS primer results as an example.

Solution

3)In automated DNA sequencing using a genetic analyser, the extension PCR products are labelled with flouroscent dyes. The labeling is done by 3´-dye labeled dideoxynucleotide terminators. The purified products in the tubes are then placed in the instrument autosampler. The samples are bought in contact with a cathode eletrode by the autosampler. The one end of a glass capillary is filled with polymer. The other end is the anode electrode immersed in buffer. As current flows, a portion of the sample enters into the capillary and flows from cathode to anode by electrokinetic injection. This electrophorosis is continued with current. When the nucleotides reach the detector, the laser excites the fluorescent dye labels. The floroscence emitted from the dyes is collected by the CCD camera and data is interpreted by the computer and the result is displayed as peaks in the chromatogram.

4) False.

PCR is very sensitive but need to be optimised. Higher concentration of template leads to nonspecific amplification leading to multiple bands or smears.