Question

__________ is a second mutation that compensates for the effect of an original, first mutation. Choose the most appropriate option from the below-mentioned options to fill in the gap.

• A. Forward mutation
• B. Supplementary mutation
• C. Suppressor mutation
• D. Compensatory mutation

Hint:

Do not confuse a suppressor mutation with a reversion.
- A reversion corrects the original mutated site back to the wild-type sequence.
- A suppressor mutation preserves the original mutation but introduces a second mutation elsewhere to restore function.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Mutations are changes in the nucleotide sequence of an organism's genome.
If a primary mutation disrupts gene function and alters the phenotype, a subsequent second mutation can sometimes restore the original wild-type phenotype.

Step 3: Detailed Explanation:
Let us review the genetic definitions of the options:
Suppressor mutation: This is a second mutation that occurs at a site distinct from the original mutation.
It suppresses or compensates for the phenotypic effects of the first mutation, restoring the wild-type phenotype.
Suppressor mutations are classified as:
- Intragenic: Occurring within the same gene as the first mutation (e.g., restoring a reading frame shifted by an insertion or deletion).
- Intergenic: Occurring in a completely different gene (e.g., a mutation in a tRNA gene that allows it to read a premature stop codon).
Let us evaluate the other options:
Forward mutation: A mutation that changes a wild-type allele into a mutant form.
Compensatory mutation is a broad evolutionary term for any mutation that reduces the fitness cost of another mutation, but "suppressor mutation" is the precise genetic term for this specific restorative event.

Step 4: Final Answer:
The second mutation that compensates for the effect of an original mutation is called a suppressor mutation, matching Option (C).