Biotechnology: Gel Electrophoresis

Using the new to improve the old….. Our knowledge of the structure and function of DNA is fairly new information. Watson & Crick - 1953 However, in a short amount of time, our DNA knowledge has been used to: Improve identification methods of criminals Determine maternity/paternity Bioengineer products Blood typing was first used for some of these purposes, but it has limited capability because it is not specific to each person.

Gel Electrophoresis (DNA Fingerprinting) Every person has a unique sequence of DNA Restriction enzymes can be used to cut a strand of DNA into several pieces e.g., enzyme cuts when it encounters GAATTC A DNA fingerprint is a unique “picture” of a person’s cut up DNA fragments that are then separated by size Who took Jimmy's lollipop?

The short version of how DNA fingerprints are made DNA is (-) charged. When you turn on the gel, the DNA samples move across to the (+) side. Because the gel is porous (contains small holes), large fragments get stuck and don’t move far whereas small fragments move farther.

Examples: Interpreting DNA Fingerprints

Example 1: Who left the blood stain? How do you know? http://www.biologycorner.com/resources/DNAfinger.gif

Example 2: Who are the children of these parents http://www.scq.ubc.ca/a-brief-tour-of-dna-fingerprinting/

Example 3: Who is the father? How do you know?

Example 4: Who are the parents of this soldier? How do you know? http://www.glencoe.com/qe/images/b136/q4318/ch13_0_c.gif