Apush Unit 5 Review

The purpose of this lab was to observe the different amount of distances each DNA samples travel when placed in a gel-electrophoresis box. Restriction endonucleases are critical tools in recombinant DNA methodology. Electrophoresis is the method of determining the size of fragments that are cut by restriction enzymes. These restriction enzymes always cut at their specific protein recognition sites. This is very useful in the sense that no two restriction enzymes codes for exactly the same recognition site, giving it a unique characteristic that is specific for a strand of DNA. Gel electrophoresis is a technique used to separate different sized fragments of DNA or RNA with the use of an electric field. When a molecule enters an electric field, the speed at which the molecule moves is influenced by several factors including: the charge of the molecule, the strength of the electrical field, the size and shape of the molecule, and the density of the medium (in this case the agarose gel) through which the molecule moves. Because of this, scientists are able to separate different groups of DNA or RNA molecules by first positioning all the molecules at a uniform starting point on the agarose gel and then placing the gel in a chamber containing buffer solution and electrodes. A buffer is a solution that adds extra ions to the gel enhancing the conductivity in the agarose gel matrix. Once in the chamber containing buffer solution and electrodes, the molecules of DNA will begin to migrate through the gel and form bands due to the negative charge of the phosphate groups in the backbone of DNA moving towards the positive electrode.

Each band consists of concentrations of homologous DNA molecule fragments which travel at the same rate and are approximately the same size. The amount of time also affects the distance between each band. The longer the amount of time the DNA molecules were electrophoresed, the greater the distance between the bands of DNA fragments because one