Chapter 21 Nucleic Acids and Protein Synthesis 21.8 Genetic Mutations
Mutations A mutation 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
Normal DNA Sequence The normal DNA sequence produces an mRNA that provides instructions for the correct series of amino acids in a protein. Correct order
Mutation: Substitution In a substitution 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
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
Genetic Diseases
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.
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.