Frameshift Mutation: Definition and Examples in AP Biology

📚 Quick Study Guide

• 🧬 Definition: A frameshift mutation occurs when the addition or deletion of nucleotides in a DNA sequence is not a multiple of three.
• 🔬 Impact: Because the genetic code is read in codons (groups of three nucleotides), these mutations alter the reading frame, leading to a completely different amino acid sequence downstream of the mutation.
• ⚠️ Types: Frameshift mutations can be either insertions (adding nucleotides) or deletions (removing nucleotides).
• 🛑 Consequences: Often result in non-functional proteins or premature stop codons, leading to truncated proteins.
• 🧪 Detection: Can be identified through DNA sequencing and analysis of protein products.
• 💡 Example: The deletion of a single 'T' nucleotide in a gene sequence, shifting the reading frame.
• 📝 Key Formula: Reading frame = $[Nucleotide\,sequence] \,mod\, 3$. A frameshift occurs when the result is not 0.

🧪 Practice Quiz

1. What is a frameshift mutation?
   1. A. A mutation that replaces one nucleotide with another.
   2. B. A mutation that inserts or deletes nucleotides in multiples of three.
   3. C. A mutation that changes the reading frame of a gene due to insertions or deletions that are NOT multiples of three.
   4. D. A mutation that only affects non-coding regions of DNA.
2. Which of the following is NOT a characteristic of frameshift mutations?
   1. A. Altered amino acid sequence downstream of the mutation.
   2. B. Can result from insertions.
   3. C. Can result from deletions.
   4. D. Always results in a functional protein.
3. If a gene sequence originally reads AUG-CCG-UAC-GGU, and a frameshift mutation causes it to read AUG-CGC-CUA-CGG-U, what type of mutation most likely occurred?
   1. A. Substitution
   2. B. Insertion
   3. C. Silent mutation
   4. D. Missense mutation
4. What is the most likely consequence of a frameshift mutation in a protein-coding gene?
   1. A. A slightly altered but still functional protein.
   2. B. A completely non-functional protein or a truncated protein.
   3. C. No change in the protein's function.
   4. D. Increased protein activity.
5. Which of the following tools would be MOST useful in identifying a frameshift mutation?
   1. A. Light microscope
   2. B. Gel electrophoresis
   3. C. DNA sequencing
   4. D. Centrifuge
6. A frameshift mutation occurs when a base is inserted into the DNA sequence ATGCGTAC, changing it to ATGCGTAG. How does this affect the resulting protein?
   1. A. It has no effect on the protein sequence.
   2. B. It causes a change in a single amino acid.
   3. C. It changes every amino acid after the insertion point.
   4. D. It causes a change to only the last amino acid.
7. Why are frameshift mutations typically more detrimental than point mutations?
   1. A. Because they always cause the protein to become longer.
   2. B. Because they shift the reading frame and alter multiple codons.
   3. C. Because they only affect the start codon.
   4. D. Because they are easily repaired by the cell.