Agronomy and Horticulture Department



Electrophoresis: How Scientists Observe Fragments of DNA

Date of this Version


Document Type



Plant and Soil Sciences eLibrary (PASSeL) Lesson


Copyright © 2002 Don Lee and Patricia Hain. Used by permission.

This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, administered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the USDA or NSF.


Describes gel electrophoresis and how the method is used in molecular genetic analysis.

Electrophoresis Overview and Objectives

This lesson describes gel electrophoresis and how the method is used in molecular genetic analysis. At the completion of this lesson, a learner should be able to:

  1. Define the terms “electrophoresis gel,” “electrophoresis buffer,” “ethidium bromide,” “fragment banding pattern,” “agarose,” and “acrylamide.”
  2. List the steps in the electrophoresis method and their proper order.
  3. Describe the basic principles and techniques involved in the use of electrophoresis to detect specific molecules and why the technique requires the geneticist to obtain or generate many copies of the molecules being detected.
  4. Contrast the electrophoresis methods used to detect DNA, RNA, and proteins.
  5. Predict how DNA analysis techniques including electrophoresis procedures would need to be changed in order to visualize specific differences between DNA samples.
  6. Determine the genotype implied at a genetic locus by the pattern of banding observed in an electrophoresis gel.
  7. Predict the electrophoresis banding pattern observed in DNA samples based on the DNA segment differences in those DNA samples.