Dna Fingerprinting Lab

Introduction

In 1968, Dr. Arber of the University of Basel in Switzerland and Dr. Smith of John Hopkins University in Baltimore discovered enzymes upon added to any DNA, resulted in the breakage of the sugar-phosphate bonds, which can also be referred to as hydrolysis, of specific nucleotide bases, or, recognition sites. DNA is made up of nitrogenous bases held together by weak hydrogen bonding. The four different bases are adenine, thymine, guanine and cytosine. The breakage results in the DNA breaking along the recognition site, the molecule turning into two pieces. These enzymes can be referred to as “cutting enzymes” or restriction endonucleases. Cutting enzymes are important because viruses have the ability to inject their DNA into bacteria. The bacteria in turn multiply the DNA but have developed restriction enzymes that modify certain DNA bases, allowing for the protection of their own DNA while destroying viral DNA. The restriction enzymes do this by searching the viral DAN for specific palindromic sequences of base pairs and cut the DNA at those sites. Two common ones are: EcoRI and PstI. If one were to add the same restriction endonuclease to two DNA fragments, the way each break can provide clues pointing to the differences in the linear base pair sequence. A stand of DNA that has been submitted to the cutting enzymes can be separated for easier observation through a process called agarose gel electrophoresis, which is a process used to separate DNA fragments based on size. Since DNA is an acid with multiple negative electrical charges, a solution made up of different sized DNA fragments are put in a small well formed in an agarose gel. With an electric current, the negatively charged DNA molecules move towards the positive electrode. The gel allows small particles to move through it because of its tiny pores, however, the larger the particles, the slower they pass through the gel. After prolonged exposure to the current, the fragments arrange themselves by size because similar sized fragments gravitate towards each other to form bands in the gel. However, DNA is not completely visible in the gel because naturally, DNA is colourless. The fragments must be stained with Fast Blast DNA stain, which is a blue stain, to show the location of these fragments. The blue stain is positively charged, therefore, it is highly attracted to the negatively charged fragments. DNA typing, DNA profiling, and DNA fingerprinting all refer to the same process of using DNA to showcase relatedness or identity. Examples of the uses of DNA typing