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

2. 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

3. 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

4. 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

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.