Biotechnology: Gel Biotechnology: Gel ElectrophoresisElectrophoresis

Using the new to improve Using the new to improve the old…..the old…..

Our knowledge of the structure and function of Our knowledge of the structure and function of DNA is fairly new information.DNA is fairly new information. Watson & Crick - 1953Watson & Crick - 1953

However, in a short amount of time, our DNA However, in a short amount of time, our DNA knowledge has been used to:knowledge has been used to: Improve identification methods of criminalsImprove identification methods of criminals Determine maternity/paternityDetermine maternity/paternity Bioengineer productsBioengineer products

Blood typing was first used for some of these Blood typing was first used for some of these purposes, but it has limited capability because purposes, but it has limited capability because it is not specific to each person.it is not specific to each person.

Gel Electrophoresis Gel Electrophoresis (DNA Fingerprinting)(DNA Fingerprinting)

Every person has a unique sequence of DNAEvery person has a unique sequence of DNA Restriction enzymes Restriction enzymes can be used to cut a can be used to cut a

strand of DNA into several piecesstrand of DNA into several pieces e.g., enzyme cuts when it encounters GAATTCe.g., enzyme cuts when it encounters GAATTC

A A DNA fingerprint DNA fingerprint is a unique “picture” of a is a unique “picture” of a person’s cut up DNA fragments that are then person’s cut up DNA fragments that are then separated by sizeseparated by size

Who took Jimmy's lollipop?

The short version of how The short version of how DNA fingerprints are DNA fingerprints are

mademade

DNA is (-) charged. When you turn on the DNA is (-) charged. When you turn on the gel, the DNA samples move across to the gel, the DNA samples move across to the (+) side.(+) side.

Because the gel is porous (contains small Because the gel is porous (contains small holes), large fragments get stuck and holes), large fragments get stuck and don’t move far whereas small fragments don’t move far whereas small fragments move farther. move farther.

Examples: Examples: Interpreting DNA Interpreting DNA FingerprintsFingerprints

Example 1: Who left the Example 1: Who left the blood stain? How do you blood stain? How do you

know?know?

http://www.biologycorner.com/resources/DNAfinger.gif

Example 2: Who are the Example 2: Who are the children of these parentschildren of these parents

http://www.scq.ubc.ca/a-brief-tour-of-dna-fingerprinting/

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

Example 4: Who are the Example 4: Who are the parents of this soldier? How parents of this soldier? How do you know?do you know?

http://www.glencoe.com/qe/images/b136/q4318/ch13_0_c.gif