A frameshift mutation is a change in DNA caused by inserting or deleting one or more nucleotides, which shifts the reading frame so that every codon after the mutation is misread, usually producing a nonfunctional protein.
A frameshift mutation happens when you insert or delete nucleotides in a gene, and that throws off the reading frame. Remember, the ribosome reads mRNA in groups of three (codons). Add or remove one base and the whole grouping shifts, so every codon after that point gets read wrong. It's like deleting one letter from a sentence and then re-splitting the rest into three-letter chunks. Everything downstream turns into gibberish.
Under EK 6.7.A.1, frameshift mutations are one of the named types you have to recognize, alongside point mutations (one base swapped) and nonsense mutations (a codon becomes a stop signal). The key thing about a frameshift is its scale. A point mutation changes at most one amino acid. A frameshift can change the entire amino acid sequence from the mutation site onward, and it often creates a premature stop codon, cutting the protein short. That's why frameshifts are far more likely to wreck a protein than a single substitution.
This term lives in Unit 6: Gene Expression and Regulation, specifically Topic 6.7 Mutations. It directly supports AP Bio 6.7.A (describe the various types of mutation) and connects to AP Bio 6.7.B, which asks you to explain how a change in genotype produces a change in phenotype. A frameshift is the clearest case of that link, because shifting the reading frame can take a working enzyme and turn it into a useless protein, changing the organism's traits. It also feeds AP Bio 6.7.C: mutations are a raw source of genetic variation, and that variation is what natural selection acts on. Whether a frameshift is harmful, neutral, or (rarely) beneficial depends on the environmental context, which is exactly the reasoning the CED wants you to apply.
Keep studying AP Biology Unit 6
Insertion and Deletion Mutations (Unit 6)
Frameshift isn't a separate cause, it's the result. Inserting or deleting nucleotides is what shifts the reading frame, so insertions and deletions ARE the events that produce frameshifts (unless they come in multiples of three, which keep the frame intact).
Point Mutation (Unit 6)
A point mutation swaps one base and changes at most one codon. A frameshift adds or removes bases and scrambles every codon downstream, which is why frameshifts usually do far more damage than a single substitution.
Cystic Fibrosis and the CFTR Gene (Unit 6)
CFTR mutations are the textbook example of genotype changing phenotype. A frameshift in CFTR can produce a completely nonfunctional chloride channel, which is a stronger phenotypic effect than a mutation that changes just one amino acid.
Genetic Variation and Natural Selection (Units 6-7)
Frameshifts are random and most are harmful, but they're still a source of new variation. Whatever variation survives is the raw material natural selection works with, tying Unit 6 mutations directly to evolution.
On multiple choice, you'll get a stem describing an insertion or deletion and have to predict the consequence. Expect questions like a frameshift in a DNA repair enzyme or in a photosynthesis enzyme, where the right answer is that the protein becomes nonfunctional and the phenotype changes. Watch for CFTR-style questions asking which mutation type would most likely produce a completely nonfunctional protein. A frameshift (or a nonsense mutation) beats a single substitution there, because it alters far more of the amino acid sequence. No released free-response question uses the term verbatim, but the reasoning shows up in any prompt asking you to connect a DNA change to a protein change to a phenotype, which is the core of LO 6.7.B. To earn the point, name the mutation type, explain that the reading frame shifts, and state that all downstream codons are misread, likely yielding a truncated or nonfunctional protein.
A point mutation substitutes one nucleotide for another and affects at most one codon (and often zero, if it's silent). A frameshift inserts or deletes nucleotides, which shifts the reading frame and misreads every codon after the mutation. The giveaway: substitution equals point, insertion/deletion equals frameshift.
A frameshift mutation is caused by inserting or deleting nucleotides, which shifts the reading frame so every codon downstream is read incorrectly.
Frameshifts usually produce a nonfunctional or truncated protein because so much of the amino acid sequence is changed, often creating a premature stop codon.
Insertions and deletions cause frameshifts unless they come in multiples of three, which preserves the reading frame.
Frameshifts cause bigger phenotypic effects than point mutations because they alter the entire sequence after the mutation site, not just one amino acid.
This term lives in Topic 6.7 and supports LO 6.7.A (types of mutation) and LO 6.7.B (genotype to phenotype).
It's a mutation caused by inserting or deleting one or more nucleotides, which shifts the reading frame so the ribosome misreads every codon after the change. It usually produces a nonfunctional protein and is one of the mutation types named in EK 6.7.A.1.
Usually, yes. A point mutation changes at most one amino acid (and can be silent), while a frameshift scrambles the entire amino acid sequence downstream and often creates a premature stop codon. That's why frameshifts are far more likely to produce a completely nonfunctional protein.
A point mutation substitutes one base for another and affects only one codon. A frameshift inserts or deletes bases, which shifts the reading frame and changes every codon after the mutation site. Substitution equals point, insertion or deletion equals frameshift.
No. If the number of nucleotides added or removed is a multiple of three, the reading frame stays intact and you just gain or lose whole codons. A frameshift only happens when the change is not a multiple of three.
Rarely, but it's possible. Whether any mutation is beneficial, detrimental, or neutral depends on the environmental context (EK 6.7.B.1). Most frameshifts are harmful because they destroy protein function, but they still add to the genetic variation natural selection acts on.