Mutation Types and Their Effects on Protein Sequence

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About This MicroSim

This MicroSim lets students apply different types of DNA mutations to a reference sequence and immediately see how each mutation affects the encoded protein. The side-by-side comparison of the original and mutated sequences makes the relationship between genotype and phenotype concrete and visual.

Mutation Types

SNP — Synonymous — A single nucleotide change that does not alter the amino acid (due to codon degeneracy). The protein is unchanged.
SNP — Missense — A single nucleotide change that substitutes one amino acid for another. The protein has a different residue at that position.
SNP — Nonsense — A single nucleotide change that creates a premature stop codon, truncating the protein.
1-bp Insertion — A single base is inserted, shifting the reading frame of all downstream codons (frameshift mutation).
1-bp Deletion — A single base is removed, causing a frameshift in the opposite direction.
3-bp Deletion — Three consecutive bases are removed, deleting one amino acid without shifting the reading frame (in-frame deletion).

Visual Encoding

Reference sequence is shown on top with bases color-coded: A (green), T (red), G (yellow), C (blue)
Mutated sequence is shown below with changed bases highlighted
Codons are grouped and translated to amino acids for both sequences
Changed amino acids are visually highlighted so students can see exactly where the protein differs

How to Use

Mutation type dropdown — Select the type of mutation to apply (SNP synonymous, missense, nonsense, insertion, deletion)
Position slider — Choose where in the DNA sequence the mutation occurs (0-indexed)
Apply Mutation button — Apply the selected mutation at the chosen position
Reset button — Return to the original reference sequence

Suggested Experiments

Apply a synonymous SNP and verify that the protein sequence is identical despite the DNA change. This demonstrates codon degeneracy.
Apply a missense SNP at the same position and compare — now a single amino acid differs.
Apply a 1-bp insertion early in the sequence and observe how every downstream codon and amino acid changes — this is the devastating effect of a frameshift.
Apply a 3-bp deletion and notice that only one amino acid is removed while the rest of the protein remains intact — this is an in-frame deletion.
Compare a nonsense SNP to a frameshift — both can truncate the protein, but by different mechanisms.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://dmccreary.github.io/bioinformatics/sims/mutation-types-explorer/main.html"
        height="522"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Grade Level

College introductory bioinformatics

Duration

15-20 minutes

Prerequisites

Understanding of DNA base pairing and the genetic code
Knowledge of codons and how mRNA is translated into protein
Basic concept of mutations as changes to DNA sequence

Activities

Exploration (5 min): Apply each of the six mutation types one at a time. For each, note: (a) how many DNA bases changed, (b) how many amino acids changed, (c) whether the protein length changed.
Guided Practice (5 min): Apply a 1-bp insertion at position 3 (early in the sequence) and then at position 15 (near the end). Compare the extent of protein damage in each case. Why does the position of a frameshift mutation matter?
Comparative Analysis (5 min): Apply a synonymous SNP, a missense SNP, and a nonsense SNP all at position 6. Rank these from least to most damaging and explain your reasoning.
Assessment (5 min): Answer the reflection questions below.

Assessment

Why can a single nucleotide change sometimes have no effect on the protein (synonymous) while other times it is catastrophic (nonsense)?
Explain why a 1-bp insertion is generally more damaging than a single-base substitution.
Why is a 3-bp deletion (in-frame) usually less damaging than a 1-bp deletion (frameshift)?
Sickle cell disease is caused by a single missense mutation in the hemoglobin gene. Use this MicroSim to explain how one amino acid change can alter protein function.