In a standard non-overlapping triplet genetic code, a single-nucleotide insertion mutation causes a frameshift that alters all downstream codons, and thus all downstream amino acids.
The diagram below contrasts a standard non-overlapping code with a hypothetical fully overlapping triplet genetic code (where each codon shares two of its bases with the next codon).
If a single-nucleotide insertion mutation were to occur within this fully overlapping code, what would be the direct consequence on the translated polypeptide?
Only a localized group of three amino acids would be altered, after which the original sequence of downstream amino acids is restored.
A permanent frameshift would still occur, altering every single codon and amino acid downstream of the insertion point.
No amino acids would be altered because the degenerate nature of the genetic code always buffers against frame changes.
Translation would immediately terminate at the site of insertion because overlapping codons are structurally incompatible with tRNA binding.
