Purpose: To investigate the process of Gel Electrophoresis in DNA fingerprinting.

Background:

Gel electrophoresis is a laboratory method used to separate mixtures of DNA, RNA, or proteins according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by an electrical field through a gel that contains small pores. The molecules travel through the pores in the gel at a speed that is inversely related to their lengths. This means that a small DNA molecule will travel a greater distance through the gel than will a larger DNA molecule.

As previously mentioned, gel electrophoresis involves an electrical field; in particular, this field is applied such that one end of the gel has a positive charge and the other end has a negative charge. Because DNA and RNA are negatively charged molecules, they will be pulled toward the positively charged end of the gel. Finally, after the DNA, RNA, or protein molecules have been separated using gel electrophoresis, bands representing molecules of different sizes can be detected.

Procedures:1. Go to the following URL:

https://www.classzone.com/books/hs/ca/sc/bio_07/virtual_labs/virtualLabs.html

2. Click on Gel Electrophoresis

3. Listen to and read the problem of the investigation

4. Now Explore the Lab Equipment used in electrophoresis

5. Complete the table below as you click on the items

Item Use (Summarize and Type the use into this table)

Agarose Gel

DNA Markers

Digested DNA SamplesElectrophoresis ChamberPower Supply

Bromophenol Blue

Gel Electrophoresis Virtual Investigation

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SCO _________RE Name: __________________________________ Lab Period: ________ Lathrop or

Waugaman

LAB #13

LIVING ENVIRONMENT 2017-2018

TBE Buffer

Gel Staining Tray

Ethidium Bromide

Micropipette

Pipette Tips

Deionized Water

Ultraviolet Light Box

6. Click on Procedure and listen to the directions.

7. Click on the Lab Notebook and type in your explanation in the box, then copy and paste your explanation into the textbox below. (Do not print the lab notebook)

8. Close the Lab Notebook and click on the procedure arrow to advance to the next step.

9. Write down what you do for each step.

Step Explanation of Procedure2

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10. Click on Lab Notebook and select the DATA tab.

11. Estimate the number of base pairs of each DNA fragment.

12. Type your answers into the computer as well as in the table below: You must complete the computer data table to be able to go to the next step.

Finished Gel from Investigation:

Analysis of Gel

Band Marker DNA(bp)

Victim DNA(bp)

Suspect 1 DNA(bp)

Suspect 2 DNA(bp)

Evidence DNA(bp)

123456789

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13. Close Lab Notebook and click on step 12.

Summary Questions:

Type your answers to the questions below. You do not need to type your answers into the computer anymore.

1. What was the purpose of the TBE buffer in electrophoresis?

2. What was the purpose of the Bromophenol Blue in electrophoresis?

3. Why does the DNA fragment move toward the positive electrode in the gel?

4. Why do a series of bands appear on the gel?

5. Why is the largest DNA fragment band found closest to the well in which the DNA was placed?

6. Why would the lab technician put the Marker DNA in the 1st WELL of the gel? In other words, what is the purpose of the Marker DNA?

7. What is true of the DNA fragment band closest to the positive end of the gel?

8. What would happen if the electrodes where plugged into the wrong outlets or ports?

9. What is used to “cut” the DNA into the different sized fragments to prepare the DNA samples before performing the electrophoresis?

10. Does the DNA found on the crime scene hair match the victim, suspect 1, or suspect 2? Explain how you know.

11. Why is DNA fingerprinting more conclusive in proving a person’s innocence rather than their guilt?