---
title: "Gene Mutations and Their Consequences"
description: "Substitutions, insertions and deletions change a gene in different ways, and only some of them change the protein. A frame shift does the most damage because every codon after it is misread."
canonical: https://lightmysky.com/learn/science/gene-mutations-and-their-consequences-mt_CDcaL6-iVp
source: https://lightmysky.com/learn/science/gene-mutations-and-their-consequences-mt_CDcaL6-iVp.md
retrieved: 2026-09-12
---

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# Gene Mutations and Their Consequences

Substitutions, insertions and deletions change a gene in different ways, and only some of them change the protein. A frame shift does the most damage because every codon after it is misread.

Subject: Science · Area: Genetics & Evolution · Ages 17 to 18
Page: https://lightmysky.com/learn/science/gene-mutations-and-their-consequences-mt_CDcaL6-iVp

## Ready when they can

- Classifies a mutation from the change in the base sequence.
- Explains why a substitution is often silent while a single deletion rarely is.
- Traces a frame shift through to the protein and says why the effect is so large.

## Lesson: Why some mutations wreck proteins

Liver and nerve cells differ by marks and factors, not by rewriting DNA. A gene mutation permanently rewrites the DNA base sequence, and its shape decides the damage. A point mutation alters a single base, most often swapping one base for another in a substitution. Insertions and deletions add or remove material, fed by spontaneous copying errors and mutagens that damage DNA or disturb copying.

Substitutions are named by their effect on the protein. Silent swaps in a codon for the same amino acid, so nothing changes. Missense swaps in a different amino acid, which matters sometimes. Nonsense makes a stop codon, cutting the protein short and usually wrecking it.

Deletions and insertions play by a harsher rule because codons run in triplets. Gain or lose a count of bases outside a multiple of three and the frame slips, rewriting every codon downstream: a frameshift. That garbles most of the protein, so one lost base usually does more harm than one swapped base. A gain or loss of exactly three keeps the frame and only adds or drops an amino acid.

**Example.** Not every mutation is a disaster. A silent change leaves the protein identical, so the cell never notices. A missense swapping similar amino acids matters little. Rarely one helps: a small regulatory tweak kept milk digestion on into adulthood and spread because it helped its carriers thrive.

**Recap.** Substitutions touch one codon while frameshifts rewrite everything downstream, so frame shifts hit hardest.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Translation at the Ribosome](https://lightmysky.com/learn/science/translation-at-the-ribosome-mt_1EdZzeqts1)
- [Mutations and Their Effect on Proteins](https://lightmysky.com/learn/science/mutations-and-their-effect-on-proteins-mt_dTOQH3vGSz)
- [Transcription Factors and Epigenetic Control](https://lightmysky.com/learn/science/transcription-factors-and-epigenetic-control-mt_nF4JJ_EDa4)

## Opens up

- [Dihybrid Crosses and the 9:3:3:1 Ratio](https://lightmysky.com/learn/science/dihybrid-crosses-and-the-9-3-3-1-ratio-mt_9IlVo04Dbt)
- [DNA Damage and the Repair Pathways That Fix It](https://lightmysky.com/learn/science/dna-damage-and-the-repair-pathways-that-fix-it-mt_r0qipp0YRR)