DNA Simulation with Paper Chromatography
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Wolf Pack in a Bottle:
DNA Simulation with Paper Chromatography

Aleta Sullivan and JoAnne Dombrowski

Target age or ability group: High School Biology.
Class time required: One 55-minute class period.
Materials and equipment: Per lab group:
    Five mock DNA solutions (different food coloring solutions)
    Filter paper (or coffee filters/paper towels)
    Scissors
    Container for water
    Five toothpicks
    Metric ruler
Summary of activity: This activity is a mock electrophoresis using paper chromatography. This activity can be used when teaching evolution, genetics, speciation, and ecology.
Prior knowledge, concepts or vocabulary necessary to complete activity: chromatography
diffusion
electrophoresis
endangered
molecular weight
species

Teacher instructions

An uncertain future awaits the red wolf, one subspecies of endangered wildlife. Geographic isolation has separated red wolf populations, and inbreeding is weakening the subspecies. Before beginning a captive breeding program, biologists conduct a wolf census and do DNA analysis to ensure species uniqueness. Many wolves in one park must be captured and transported to other areas where biologists hope that time and evolution will build up diverse populations. As wildlife conservationists learn, at times the programs intended to save animals create unexpected risks.

An animal's genetic makeup can be analyzed using a technique called restriction mapping. In this process, strands of genetic material are first attacked by enzymes that cleave the DNA at specific sites. Next, the fragments resulting from this cleavage are sorted in a chromatography-like process called electrophoresis. If samples from two organisms contain a similar assortment of DNA fragments, then the organisms are closely related. If fragment concentrations in samples are dissimilar, the organisms are less related, and these are the animals needed to strengthen the breeding program. In this activity, you will perform an experiment that models this type of DNA analysis.

Lab Notes: This activity can be performed by individuals or in groups. Make five mock DNA solutions using food coloring; three should be similar and two dissimilar. Each group or individual should have one sample of each of the five solutions.

Suggested Solutions:

Solution 1: equal amounts red, yellow, and green

Solution 2: equal amounts blue, red

Solution 3: equal amounts red, yellow, and green

Solution 4: equal amounts red, yellow, and green

Solution 5: two parts blue, one part green

(Teacher Answer to Problem: Solution 2 provides the most genetic variation, and represents the animal best for the breeding program.)

Answers to Student Questions:

1. They separate into colors as they travel up the paper.

2. DNA fragments have different weights and move at different speeds in electrophoresis.

3. and 4. Answers will vary.

5. Like solutions of DNA fragments, the food-coloring solutions separate into components. Similarities and differences in the components are then used to classify the solutions. Solutions that show similarities are analogous to restriction mapping of closely related species; dissimilar solutions represent distant relations.

6. Answers will vary depending upon setup, but the best wolf is represented by teacher Solution 2.

7. Introducing two different subspecies may provide genetic variety. The hoped-for outcome is a wolf pack in which genetic variety may insure species survival.

Extensions

A similar activity can be found in Scientific American Frontiers Show #503, Science Italian Style, All in the Family segment (running time 10:55).

Additional WOLF materials available through your state Project WILD Coordinator.

Wolf Pack in a Bottle

Purpose: to determine which wolf is more genetically different for the breeding program.

Procedure:

1. Gather your supplies and samples. Observe the samples and predict which one will be the best wolf (the most different). Answer on your data sheet.

2. Cut filters 10 cm wide and 10 cm long. Fold paper so that it will stand in container (see diagram).

3. Draw a pencil line about 2 cm above the lower edge of the filter paper. Mark five locations on the line, evenly spaced, and number these locations below the line.

4. Using a new toothpick for each solution, transfer mock DNA Solutions 1-5 to marked locations. Let the solutions dry.

5. While filter paper dries, pour about 1 cm of water into the container.

6. Position the folded filter paper in the water container so that the treated end is in contact with the water (the dots should be about 1 cm above the surface of the water).

7. After 15 minutes, examine the paper. Compare your samples of DNA Solutions 1-5. Then compare your samples with others in your class.

8. Answer question on Data Sheet.


NamePeriod Class:


Student Data Page

Prediction:







1. Sketch your experiment design.







2. Attach filter paper sample to this data page.







Questions

1. What happens to the sample drops?



2. Why are we able to separate differences in DNA?



3. Which samples have a similar makeup?



4. Which samples appear dissimilar?



5. How can you apply your observations to restriction mapping?



6. Which sample represents the best wolf for the breeding program? Why?



7. Why would scientists introduce two different red wolf subspecies? What is the hoped-for outcome?

CONSIDER THIS!

It is estimated that more than 99% of the species ever living on Earth are now extinct. How much should people do to preserve living species?



Should endangered species always be rescued, despite the risks? Who should determine which species are saved?



Why is inbreeding a serious problem? How has inbreeding affected the cheetah?



Are there any endangered species in your area which might benefit from this breeding program?




On to The Electrophoresis
of Human Hemoglobin

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