Mutations are any changes in the sequence of nitrogenous bases in DNA. There are several types of mutations including missense, nonsense, silent, point, and frameshift mutations. Point mutations involve changing a single base through substitution, insertion, or deletion. Frameshift mutations are caused by insertions or deletions and shift the reading frame, altering the entire amino acid sequence.

1. Unit 6 Notes:
Mutations

2. (1) What Are Mutations?
• Mutations: Any change in the sequence of
nitrogenous bases.
• Types:
– Missense vs. Nonsense
– Point (Substitution, Deletion, Insertion)
– Frameshift
• Causes:
– Cell errors
– Chemical / UV exposure

4. (2) Types of Mutations
• Missense: Mutation changes type of protein made.
• Nonsense: Mutation causes premature stop in
translation.
• Silent: Changes bases, but has no effect on protein made.
• Point: Change 1 base along DNA sequence.
– Substitution  Replace 1 base with a different one.
– Insertion  Add 1 extra base into sequence.
– Deletion  Remove 1 base from the sequence.
• Frameshift: Any Insertion or Deletion mutations which
shift the bases, changing the amino acid sequence.

7. (3) Mutation Examples:
DNA Template: TAC—GCG—AAA—ACT
1. Insertion:
2. Deletion:
3. Substitution:
4. Which of the above is/are Frameshift?
5. Which of the above is/are missense?
6. Which of the above is/are nonsense?