Answer:
The answer is "Substitution of one nucleotide ".
Step-by-step explanation:
Replacement mutant is a kind of DNA replication mistake placing faulty nucleotide or nucleotide sequences in the wrong positions. A nucleotide sequence substitutes for just a type of substitution mutant, a spots gene.
A researcher observed that a specific mutation did not affect a gene-encoded polypeptide. This mutation was presumably the replacement of the nucleotide.