Core Genetics & Mechanisms

Gain-of-Function vs. Loss-of-Function Mutations

A gain-of-function mutation increases or creates a new activity for a gene or protein, while a loss-of-function mutation reduces or abolishes normal function. Both mutation types play central roles in disease biology and are critical tools in genetic research.

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Overview

Genetic mutations can influence how a protein behaves in a cell—not just whether it is present, but how much of it is produced, how active it is, or what it does. Gain-of-function mutations enhance normal activity or create new functions, while loss-of-function mutations reduce or eliminate normal gene product function.

Frequently Asked Questions

Can the same mutation be both gain- and loss-of-function?

Not the same mutation, but different mutations in the same gene can have opposite effects—one increasing protein activity, another eliminating it.

How do researchers determine if a mutation is gain-of-function or loss-of-function?

Researchers use biochemical assays, signaling readouts, and phenotype characterization in cell or mouse models to assess whether a mutation increases, reduces, or abolishes function.

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Knockin Mouse Models Conditional Knockout Mouse Models

Related Terms

Point Mutation

A single-nucleotide change in a DNA sequence that can modify how a gene is expressed or how its protein product functions. Even a one-base change can dramatically alter phenotype, making point mutations crucial to understanding genetic disease, evolution, and therapeutic intervention.

Knockout (KO) Mouse Models

A genetically engineered mouse in which a specific gene has been permanently inactivated ('knocked out') to study its biological function, role in disease, and potential as a therapeutic target.

Knockin (KI) Mouse Models

A genetically engineered mouse in which a specific DNA sequence—such as a gene, cDNA, mutation, reporter, or human ortholog—is inserted into a defined genomic locus to add or modify gene function.

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