The first technique discovered for modifying DNA was the Recombinant DNA method. Today this technique is still used as it is relatively simple.

1. First the DNA is "cleaved" into fragments using a restriction enzyme.

2. The fragments of DNA are then inserted into Plasmids or viral DNA which have been cleaved with the same restriction enzymes as the original source DNA.

3. The plasmids or viruses serve as carriers allowing the foreign DNA to be inserted into the host cell. Host cells are usually, but not always, bacteria. (Living world, 215). As each host cell reproduces, it clones itself thus forming a large number of recombinant DNA filled cells.

4. Last, the cells must be screened to determine which contains the proper sequence of recombinant DNA. This is often the most difficult stage in genetic engineering.

A valuable technique in that it allows the scientist to create millions of exact copies of a specific genetic sequence thus making studying of a gene much easier.

1. The DNA sequence is heated, causing the bonds to break down and the strands to separate.

2. Single stranded primers stick to the separated strands when cooled. The original strands do not reform because of the large number of primers.

3. the DNA then adds nucleoties to the ends of the primers, forming copy's of the original strands. Soon the reformed strands double into identical strands.

A technique for separating DNA segments of different lengths from each other thus allowing the researcher to separate the specific strand of interest from the excess produced in DNA techniques.

1. DNA fragments are placed into a thick jello like gel usually made from seaweed called Agarose.

2. A current is then passed through the gel which pulls the DNA through the gel toward the positive connection.

3. The DNA must move through the gel, the larger pieces taking longer to move through the gel. Thus the smaller pieces end up closer to the positive pole while the longer pieces remain near the original infusion spot.

4. When the gel is passed under a black light, the longer DNA glows, showing clearly defined regions for the different length segments.

A simple diagram of Electrophoresis and how it works. The blue represents the gel and the white lines the DNA segments. The positive pole (+) draws the smaller portions of DNA through the gel leaving the longer near the negative (-) pole.

Made famous by the O.J. Simpson trial and first used in 1987, DNA fingerprinting has revolutionized the United States legal system. All a lab technician needs is a drop of blood or a single hair left at a crime scene to make a match.

Southern Blot Test

The Southern blot test is the "average" DNA fingerprinting test that you are probably the most familiar with. You may even have analyzed Southern Blot test results if you took Intro to Biology at Lock Haven University.

1. The DNA is separated from the rest of the cell structure

2. Restriction Enzymes are used to cut the DNA into segments

3. The segments are then put through Electrophoresis to separate them by size.

4. The segments are then heated so they separate into single strands (similar to PCR Amplification)

5. The gel with the size sorted DNA is then applied to paper and baked to attach the DNA to the paper.

6. A radioactive probe is then made of the results (basically this consists of exposing the DNA segments to radiation so they they will show certain patterns in the DNA thus allowing for easier identification)

A DNA Fingerprint after being exposed to a radioactive probe. Scientists would then look for matching patterns between samples in order to get a match.