Lab 10: Biotechnology
Part 1: DNA Fingerprinting
- To isolate DNA from wheat germ
- To simulate gel electrophoresis for creating a DNA fingerprint
- 50 ml test tube (supplied to you)
- wheat germ (found in the test tube; FOR LAB USE ONLY – DO NOT CONSUME)
- liquid detergent
- rubbing alcohol (70% isopropyl alcohol)
- measuring spoons
- paper clip that is “unbent” to hook out the DNA (or any other object with a hook on it such as a crochet needle)
Description of the problem
All individuals (except identical twins) have a unique DNA fingerprint. By isolating DNA and undergoing gel electrophoresis, a DNA fingerprint can be made. Among other things, DNA fingerprinting can be used to identify criminals, exonerate suspects, test for paternity, identify unknown individuals whose bodies have been partially degraded, follow inheritance patterns, and study the population structure of wild organisms.
Experiment: Isolating DNA
You will isolate DNA from wheat germ and create a virtual DNA fingerprint. (Note: because the FBI often has only old and/or degraded DNA samples to work with, they rely on more complex methods to isolate the DNA.)
1. Place 1 teaspoon of raw wheat germ (toasted wheat germ won’t work) in a 50 ml test tube.
2. Add 1 tablespoon of hot (50-60 °C) tap water and mix constantly for 3 minutes.
3. Add ¼ teaspoon of liquid detergent and mix gently every minute for 5 minutes. Try not to create foam. (The following liquid soap products can be used: Lemon Fresh Joy, Woolite, Ivory, Shaper, Arm & Hammer, Herbal Essence shower gel by Clairol, Tide, Dish Drops, Kool Wash, Cheer, Sunlight Dish Soap, Dawn, Delicate, All, or Ultra Dawn. Powdered detergents don’t work well.)
4. If necessary, use a piece of paper towel to remove any foam from the top of the solution.
5. Tilt the test tube at an angle. SLOWLY pour 1 tablespoon of rubbing alcohol down the side so that it forms a layer on top of the water/wheat germ/detergent solution. Don’t mix the two layers together. DNA precipitates at the water-alcohol interface; therefore, it’s crucial to pour the alcohol very slowly so that it forms a layer on top of the water solution. If the alcohol mixes with the water, it will become too dilute and the DNA won’t precipitate.
6. Let the test tube sit for a few minutes. White, stringy, filmy DNA will begin to appear where the water and alcohol meet.
7. Use the paper clip to GENTLY swirl the wheat germ mixture. As you gently swirl, start lifting the clip out of the test tube (continue to swirl through the alcohol layer as you lift the clip out). Some of the stringy, snot-like DNA will adhere to the paper clip.
1. What, specifically, is wheat “germ”? Why won’t flour work as a DNA source? (Hint: investigate how flour is made.)
PLEASE CLEAN THE TEST TUBE BEFORE RETURNING THE LAB KIT.
Simulating the process of creating a DNA fingerprint
DNA fragments are separated using gel electrophoresis and visualised after the gel is stained.
Simulate this process by clicking here.
2. In your simulation exercise (see the above link), what were the estimated lengths (in base pairs, or bp) of the DNA fragments in your sample?
Part 2: Gene Therapy, Stem Cell Research, and Cloning
- To investigate the techniques of gene therapy, stem cell research, and cloning
- None, as it’s completely online
Description of the problem
Gene therapy, stem cell research, and cloning are all techniques that can be used to treat human diseases. Gene therapy is the process of replacing defective genes with healthy ones. Stem cells are undifferentiated cells that can give rise to specialized cell types throughout the body. Therapeutic cloning involves transferring the nucleus from a somatic cell into an egg cell whose own nucleus has been removed. Its goal is to harvest stem cells that can be used to treat diseases.
3. Write a thoughtful essay discussing your opinions on the use of these techniques. Your discussion may include, though is not limited to, answering such questions as:
(a) Should the use of these techniques be widespread, limited, or nonexistent and why? If limited, what are the appropriate circumstances for their use? What are inappropriate circumstances for their use?
(b) How much money should be spent on these techniques and their applications? Keep in mind that for every dollar spent on these research techniques, there is one less dollar spent elsewhere, such as in neonatal care.
(c) Should genetic information be withheld from insurance companies? If not, will insurance companies be able to deny coverage to a patient with a particular disease?