Question

Which type of mutation shifts the reading frame of all downstream codons?

Options

• Deletion mutation only

• Frameshift mutation

• Substitution mutation

• Point mutation

Answer 1

A frameshift mutation, caused by insertion or deletion of base pairs, shifts the reading frame of all downstream codons. The classic example is a frameshift in the β-globin gene, where the loss or gain of nucleotides alters how the genetic code is read, affecting all subsequent amino acids in the protein sequence.