Mutations: Changing the Genetic Code

Interactive, scaffolded model

Overview and Learning Objectives

Students compare the effect of several different types of mutations in DNA, including nucleotide substitution, nucleotide insertion, and nucleotide deletion.

Students will be able to:

• demonstrate how substituting one nucleotide for another often makes no significant change in the shape of a peptide chain, unless it occurs at a critical location;
• explain the connection between hydrophobia and the impact of certain mutations.

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Classroom Practice

In this activity students can edit a DNA nucleotide sequence and observe how it will affect the sequence of amino acids in the protein and the shape of the resulting protein. With this notion, they can generate different mutations. For example, by inserting or deleting a nucleotide, they create a frameshifting mutation, and compare the effect with less dramatic substitution mutations. Students reinforce the idea that frameshift mutations typically lead to multiple changes in the amino acid sequence and the appearance of a non-functional protein. If the protein were essential for the living cell, such a mutation would be lethal.

A mathematical codon exercise can help students figure out the redundancy concept of the codons. Ask your students to figure out how many three-letter "words," such as AAA or ATA etc. can be made from four letters A, T, C, and G. To start, you might help them discover for themselves that there are 16 possible "words" beginning with A. The same must be true for words beginning with G, T, and C, for a total of 16+16+16+16 or 64 different words.

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Central Concepts

Key Concept:

Mutations in DNA can result in changes in the sequence of amino acids of a protein (its primary structure). Mutations may lead to changes in protein structure, in the way a protein functions, and can become the molecular cause of illness. Due to the redundancy of the genetic code, many changes have no effect.

Additional Related Concepts

Concept Map Available

Biology

• Adaptation
• Sickle Cell Anemia

Molecular Biology

• Mutation

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Textbook References

• Biology (Miller and Levine) Prentice Hall 5th Edition - Unit 2: Chapter 10 - Genes and Chromosomes
• Biology (Miller and Levine) Prentice Hall 5th Edition - Unit 2: Genetic Engineering
• Biology (Miller and Levine) Prentice Hall 5th Edition - Unit 3: Chapter 9 - Introduction to Genetics
• Biology: Concepts and Connections (Pearson) 5th Edition - Chapter 13: How Populations Evolve
• Biology: Concepts and Connections (Pearson) 5th Edition - Chapter 26: Chemical Regulation
• BSCS Blue (8th Edition) - Chapter 9: Expressing Genetic Information
• Web of Life - Chapter 7: DNA, Genes and Chromosomes
• Web of Life - Chapter 8: Protein Synthesis
• Web of Life - Chapter 9 The Biotechnology Revolution

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Benchmarks and Standards

AAAS

• THE LIVING ENVIRONMENT: CELLS - Gene mutation in a cell can result in uncontrolled cell division, called cancer (Full Text of Standard)
  
  
• THE LIVING ENVIRONMENT: HEREDITY - Gene mutations can be caused by such things as radiation and chemicals (Full Text of Standard)
  
  

NSES

• Life Science: Heredity Molecular Basis - 1 In all organisms, the instructions for specifying the characteristics of the organism are carried in DNA (Full Text of Standard)
  
  
• Life Science: Heredity Molecular Basis - 3 Changes in DNA (mutations) occur spontaneously at low rates (Full Text of Standard)
  
  

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Extensions and Connections

An activity that looks specifically at the molecular basis for Sickle Cell Anemia can be found at

http://molo.concord.org/database/activities/281.html

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Activity Credits

Created by CC Project: Molecular Workbench using Molecular Workbench

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Requirements

• Java 1.5+ - Java 1.5+ is available for Windows, Linux, and Mac OS X 10.4 and greater. If you are using Mac OS X 10.3, you can download MW Version 1.3 and explore within it instead.

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