Difference Between Intragenic and Extragenic Suppressor Mutation

The key difference between intragenic and extragenic suppressor mutation is that intragenic suppressor mutation is a suppressor mutation that occurs within the same gene. In contrast, an extragenic suppressor mutation is a mutation which occurs in a different gene.

A mutation is an alteration of the nucleotide sequence of a gene. Suppression mutation is a second mutation that suppresses the phenotypic effect of the first mutation. Suppression mutation occurs at a site distinct from the first mutation. It can restore the original function of the mutated gene. There are two types of suppression mutations. They are intragenic suppression mutation and intergenic (extragenic) suppression mutations.

1. Overview and Key Difference
2. What is Intragenic Suppressor Mutation
3. What is Extragenic Suppressor Mutation
4. Similarities Between Intragenic and Extragenic Suppressor Mutation
5. Side by Side Comparison – Intragenic vs Extragenic Suppressor Mutation in Tabular Form
6. Summary

What is an Intragenic Suppressor Mutation?

Intragenic suppressor mutation is one of the two types of suppression mutation. As the name suggests, the suppressor lies within the same gene of the first mutation. Therefore, the second mutation occurs within the same gene to alleviate or reverse the original mutation’s phenotypic effect.

Difference Between Intragenic and Extragenic Suppressor Mutation

Figure 01: Suppressor Mutation

There are several mechanisms through which intragenic suppressor mutations take place. They include the same-site replacement, compensatory mutation, alteration in splicing, and reversion of dominant mutations by cis-knockout. In most intragenic suppressor mutations, the mutation happens in a different nucleotide in the same triplet in a way that the codon encodes the original amino acid.

What is an Extragenic Suppressor Mutation?

Extragenic suppressor mutation or intergenic suppressor mutation is the second type of suppression mutation. In this type of mutation, the suppressor lies in a different gene compared to the gene of the first mutation. Extragenic suppression mutation can occur in various ways such as alterations in splicing, translation or nonsense-mediated decay. Moreover, they can occur via bypass, dosage effects, product interaction, or removal of toxic products. Most extragenic suppressor mutations result in a product which can compensate for the dysfunction in the first mutation. Extragenic suppressor mutations are useful in identifying and studying interactions between molecules like proteins.

What are the Similarities Between Intragenic and Extragenic Suppressor Mutation?

Intragenic and extragenic suppressor mutations are two types of suppression mutations.
They are second mutations which occur at a site distinct from the location of the first mutation.
Both types of mutations suppress the phenotypic effect of the first mutation.
In other words, both types of mutations are able to restore the phenotype seen prior to the original background mutation.

What is the Difference Between Intragenic and Extragenic Suppressor Mutation?

Suppressor mutation is a second mutation that restores the function of a gene lost by a first mutation. A suppressor mutation that occurs within the same gene is known as intragenic suppressor mutation while a mutation which occurs in a different gene is known as extragenic suppressor mutation. So, this is the key difference between intragenic and extragenic suppressor mutation.

Below is a summary of the difference between intragenic and extragenic suppressor mutation in tabular form.

Summary – Intragenic vs Extragenic Suppressor Mutation

Suppression mutations are second mutations that correct the original function of a mutated gene. Intragenic suppressor mutation occurs within the same gene where the original mutation occurred and restores the wild type phenotype. Extragenic suppressor mutation takes place in a different gene and corrects the phenotypic effect of the first mutation. Thus, this is the key difference between intragenic and extragenic suppressor mutation.

Reference:

“Genetic Suppression*.” WormBook Header Image, Available here.
“Suppressor Mutation.” Wikipedia, Wikimedia Foundation, 12 Dec. 2020, Available here.

Image Courtesy:

1. “Oncogene and tumour suppressor gene” By Philippe Hupé – Emmanuel Barillot, Laurence Calzone, Philippe Hupé, Jean-Philippe Vert, Andrei Zinovyev, Computational Systems Biology of Cancer Chapman & Hall/CRC Mathematical & Computational Biology, 2012, (CC BY-SA 3.0) via Commons Wikimedia