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Chapter 21 Nucleic Acids and Protein Synthesis

Explore the role of genetic mutations in altering DNA sequences, resulting in incorrect codons and amino acids. Learn about mutagens, genetic diseases, and how to identify substitution and frame shift mutations.

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Chapter 21 Nucleic Acids and Protein Synthesis

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  1. Chapter 21 Nucleic Acids and Protein Synthesis 21.8Genetic Mutations

  2. Mutations Amutation • alters the nucleotide sequence in DNA • results from mutagens such as radiation and chemicals • produces one or more incorrect codons in the corresponding mRNA • produces a protein that incorporates one or more incorrect amino acids • causes genetic diseases that produce defective proteins and enzymes

  3. Normal DNA Sequence • The normal DNA sequence produces an mRNA that provides instructions for the correct series of amino acids in a protein. Correctorder

  4. Mutation: Substitution In asubstitution mutation, • a different base substitutes for the proper base in DNA • there is a change in a codon in the mRNA • the wrong amino acid may be placed in the polypeptide Incorrect order Wrong amino acid

  5. Mutation: Frame Shift In a frame shift mutation, • an extra base adds to or is deleted from the normal DNA sequence • the codons in mRNA and the amino acids are incorrect from the base change Incorrect amino acids

  6. Genetic Diseases

  7. Learning Check Identify each type of mutation as a substitution (S) or frame shift (F). A. Cytosine (C) enters the DNA sequence. B. One adenosine is removed from the DNA sequence. C. A base sequence of TGA in DNA changes to TAA.

  8. Solution Identify each type of mutation as a substitution (S) or frame shift (F). F A. Cytosine (C) enters the DNA sequence. F B. One adenosine is removed from the DNA sequence. S C. A base sequence of TGA in DNA changes to TAA.

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