Gene Mutations and Proteins

Name:

Date:

📚 Part 1: Multiple Choice & Matching

1. A point mutation that changes one codon so a different amino acid is incorporated is called:

Silent mutation

Missense mutation

Nonsense mutation

Frameshift mutation

2. Deleting two nucleotides from the coding sequence is most likely to cause:

A silent change with no amino acid change

A missense mutation only

A frameshift that alters many downstream amino acids

Duplication of a codon

3. Which mutation most often produces a shortened (truncated) protein?

Missense mutation

Silent mutation

Nonsense mutation

Insertion of three nucleotides

4. Check all factors that can increase the rate of mutations:

UV radiation

X-rays and other ionizing radiation

Certain chemicals (mutagens)

Routine proofreading by DNA polymerase

5. Match each mutation type (left) with a likely effect on the protein (right). Draw a line to match.

A. Silent mutation

B. Missense mutation

C. Nonsense mutation

D. Frameshift mutation

1. Introduces a premature stop codon → shortened protein

2. Changes one amino acid; protein may work differently

3. Alters reading frame; most downstream amino acids change

4. No change in amino acid sequence

✏️ Part 2: Short Answers & Modeling

6. Below is a short coding DNA sequence (5' → 3'). Transcribe to mRNA and translate to amino acids (write three-letter abbreviations). Show mRNA codons and the amino acid sequence.

DNA coding strand: ATG GAA TTT GGC TGA

7. If the second codon (GAA) mutates to UAA in the mRNA, what type of mutation is this and what immediate effect does it have on the protein?

8. Explain in 2–3 sentences how an early frameshift mutation can affect protein structure and the organism's traits (function/phenotype).

9. Design a brief classroom model to show the difference between a substitution and a deletion mutation and how each affects the protein product. List 3 simple materials and write one sentence describing what students will observe.