Agronomy and Horticulture Department



Gene Expression Part 2: Expression of Herbicide Resistant ALS Genes in Plants

Date of this Version


Document Type



Plant and Soil Sciences eLibrary (PASSeL) Lesson


Copyright © 2003 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.

Development of this lesson was supported in part by Cooperative State Research, Education, & Extension Service, U.S. Dept. of Agriculture under Agreement Number 98-EATP-1-0403 administered by Cornell University and the American Distance Education Consortium (ADEC). Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.


Overview and Objectives for Gene Expression Part 2

This lesson describes how changes in the DNA sequence of a gene can alter the synthesis of a protein and thus influence traits such as herbicide resistance.

In this lesson we will describe how changes in the gene can alter the gene expression process and influence traits in an organism. The specific example of ALS-inhibitor herbicide resistance is used to demonstrate the impact of genetic change on trait expression in a plant.

At the completion of this lesson you should be able to:

  1. Explain how a mutation in a single gene can control resistance to herbicides such as ALS inhibitors.
  2. Predict the impact of a specific mutation on gene expression and the eventual trait observed in a plant.
  3. Distinguish between the molecular and classical definitions of an allele.
  4. Describe the molecular basis of dominance or a lack of dominance between alleles.