Practice question

Codon periodicity is three nucleotides, therefore deleting exactly three base pairs removes one amino acid while maintaining original reading frame downstream of lesion. Translation proceeds with correct phase after deletion, producing protein missing single residue but otherwise colinear with wild-type sequence. Such in-frame deletions often retain partial activity depending on location in secondary structure, whereas deletion of one or two nucleotides would shift frame. This principle explains prevalence of viable three-base polymorphisms in population databases and distinction between frameshift and in-frame variants.