gen-define-a-frameshift-mutation-and-give-one-short-worked-examp-e55b

Define a frameshift mutation and give one short worked example.

# Frameshift Mutation ## Definition A **frameshift mutation** is a genetic mutation caused by insertions or deletions (indels) of nucleotides in a DNA sequence that are not in multiples of three. This shifts the reading frame of codons during translation, typically resulting in a completely different and nonfunctional protein downstream of the mutation. ## Worked Example **Original DNA sequence:** ``` DNA: ATG|GAA|CTG|TTC|AAG|TAA mRNA: AUG|GAA|CUG|UUC|AAG|UAA Met-Glu-Leu-Phe-Lys-STOP ``` **After deletion of one nucleotide (A) at position 4:** ``` DNA: ATG|GGA|CTG|TTC|AAG|TAA ↑ deletion occurs here mRNA: AUG|GGA|CUG|UUC|AAG|UAA Met-Gly-Leu-Phe-Lys-STOP ``` Wait, let me correct this: **After deletion of one nucleotide (A) at position 5:** ``` DNA: ATG|GCT|GTT|CAA|GTA|A ↑ 'A' deleted, frame shifts mRNA: AUG|GCU|GUU|CAA|GUA|A Met-Ala-Val-Gln-Val-... ``` The reading frame shifts, producing completely different amino acids from the mutation point onward, usually resulting in a nonfunctional protein or premature stop codon.