The key difference between back mutation and suppressor mutation is that the back mutation reverses the mutant genotype into the original, normal wild type while the suppressor mutation suppresses the primary mutation by producing the functional protein products inhibited by the primary mutation.
Mutation is an alteration of the nucleotide sequence of a DNA molecule in the genome of a particular organism. Hence, mutations occur due to errors take place during the mitosis and meiosis and also due to various factors such as radiation, chemicals, etc. The most common type of mutations is the forward mutations. It is kind of a primary mutation. Forward mutation changes the wild-type normal genotype to a mutant genotype. Accordingly, depending on the type of mutation, its effect varies. However, some mutations can correct the effects of primary mutations. Back mutation and suppressor mutation are two such types of mutation. They involve in reversing the effects of the primary mutation.
CONTENTS
1. Overview and Key Difference
2. What is Back Mutation
3. What is Suppressor Mutation
4. Similarities Between Back Mutation and Suppressor Mutation
5. Side by Side Comparison – Back Mutation vs Suppressor Mutation in Tabular Form
6. Summary
What is Back Mutation?
A back mutation or reverse mutation is a condition where the mutant genotype changes to the original wild type. Consequently, this process completely reverses the normal forward mutation. This type of mutations could be clearly observed in auxotrophic microorganisms where they revert to phototrophs. This is very clear when the cells of original auxotrophic strains are plated in minimal media and observed. This ability of mutated genes to reverse to its original wild type, suggests the fact that, in some cases of mutations, it is not a permanent process, but reversible.
Furthermore, back mutations occur under different pathways. In a true back mutation, restoration of the original base pair sequence takes place. Therefore, if a GC pair of the original wild-type genome sequence is replaced by an AT pair in the process of a forward mutation, a true back mutation could again substitute a GC pair at the same position.
Figure 01: Mutation
Nevertheless, in some forward mutations, a different base pair is inserted at the site of the altered pair. If when AT replaces GC, the back mutation may occur with the substitution of CG instead of GC. Such a phenomenon will result in a reverse phenotype although the sequence is different from the original wild-type sequence in a single base pair.
What is Suppressor Mutation?
A suppressor mutation is a type of the second mutation where it restores a function lost by a primary mutation. Suppressor mutations are of two types; they are the intragenic suppressor mutation and intergenic suppressor mutation. Moreover, suppressor mutations arise under different pathways. Intragenic suppressor mutation (a second mutation) occurs within the gene that lies the first mutation but in a different site. On the other hand, intergenic suppressor mutation occurs in a different gene which doesn’t contain the first mutation.
However, during both intragenic and intergenic suppressor mutations, a common effect takes place. That is, both types of second mutations (intragenic and intergenic) synthesize the functional products of the gene that was interrupted by the first mutation. For example, if the primary mutation within gene X inhibits the production of protein X, the suppressor mutation that occurs within the same gene or different gene will result in producing the protein X. As a result, this process reverses the effect of the gene X mutation in indirectly.
What are the Similarities Between Back Mutation and Suppressor Mutation?
- Back mutation and suppressor mutation are types of secondary mutations.
- Both affect the primary mutation directly.
- Also, both function to reverse the effect of the primary mutation.
What is the Difference Between Back Mutation and Suppressor Mutation?
Back mutation and suppressor mutation are two types of mutations that reverse the effect of the primary mutations. Back mutation changes the mutant phenotype back into the wild-type phenotype. Suppressor mutation corrects the effect of primary mutation by producing the product of the mutated gene. Therefore, this is the key difference between back mutation and suppressor mutation.
Furthermore, back mutation corrects the mutated gene while suppressor mutation does not correct the gene. Instead, it produces the protein product that was blocked due to the primary mutation. Thus, this is another difference between back mutation and suppressor mutation.
The below infographic presents more details on the difference between back mutation and suppressor mutation.
Summary – Back Mutation vs Suppressor Mutation
Forward mutations change the wild-type normal genotype into a mutant type. Both back mutations and suppressor mutations reverse the effects of the primary mutation directly or indirectly. Back mutation or reverse mutation is a condition where the mutant genotype changes to the original wild type. On the other hand, suppressor mutation is a type of the second mutation which can restore the function lost by a primary mutation. In suppressor mutation, the primary mutation prevails but indirectly suppresses it, where it masks the phenotypic effects of the primary mutation. Hence, this is the difference between back mutation and suppressor mutation.
Reference :
1.“Biology Notes on Reverse Mutations | Genetics.” Biology Discussion, 12 Dec. 2016. Available here
2.“Back Mutation.” The Columbia Encyclopedia, 6th Ed, Encyclopedia.com, 2018. Available here
3.“Suppressor Mutation.” The Columbia Encyclopedia, 6th Ed, Encyclopedia.com, 2018. Available here
Image Courtesy:
1.”Benzopyrene DNA adduct 1JDG”By Zephyris, (CC BY-SA 3.0) via Commons Wikimedia