Frameshift mutation

Definition

A frameshift mutation is a genetic alteration where nucleotides are added or deleted from the DNA sequence in a number that is not divisible by three, disrupting the normal reading frame of the genetic code. This type of mutation can lead to significant changes in the amino acid sequence of the resulting protein, often resulting in nonfunctional proteins or premature stop codons. The consequences of frameshift mutations can drastically affect an organism's phenotype and are an important aspect when considering how mutations occur and are repaired in DNA.

5 Must Know Facts For Your Next Test

1. Frameshift mutations can be caused by insertions or deletions of one or more nucleotides in a DNA sequence.
2. Since frameshift mutations alter the reading frame of codons, they typically have more severe consequences than point mutations.
3. The resulting protein from a frameshift mutation may differ greatly from the original protein, often resulting in loss of function.
4. Frameshift mutations can lead to diseases, such as cystic fibrosis and certain forms of cancer, due to the production of dysfunctional proteins.
5. Cells have several DNA repair mechanisms, like nucleotide excision repair and mismatch repair, which help fix frameshift mutations when they occur.

Review Questions

• How does a frameshift mutation differ from a point mutation in terms of genetic impact?
  • A frameshift mutation significantly alters the reading frame of the genetic code due to the insertion or deletion of nucleotides in numbers not divisible by three. This can lead to an entirely different amino acid sequence downstream from the mutation, often resulting in a nonfunctional protein. In contrast, a point mutation affects only a single nucleotide and may result in a silent, missense, or nonsense mutation without changing the overall reading frame.
• Discuss the potential consequences of frameshift mutations on protein synthesis and function.
  • Frameshift mutations can lead to drastic changes in protein synthesis since they alter the codon reading frame. This change may produce proteins that are completely different from what was originally intended, possibly leading to truncated proteins due to premature stop codons. The dysfunctional proteins resulting from these mutations can disrupt normal cellular functions and contribute to various genetic disorders.
• Evaluate the role of DNA repair mechanisms in mitigating the effects of frameshift mutations and maintaining genomic integrity.
  • DNA repair mechanisms play a crucial role in correcting errors like frameshift mutations that occur during DNA replication or due to external factors. Mechanisms such as mismatch repair and nucleotide excision repair can identify and rectify these errors before they become permanent changes. By effectively repairing these mutations, cells maintain their genomic integrity, reducing the risk of diseases associated with uncorrected frameshifts, such as cancer.

Related terms

Codon: A codon is a sequence of three nucleotides in DNA or RNA that corresponds to a specific amino acid or a stop signal during protein synthesis.

Point Mutation:

A point mutation is a change in a single nucleotide base pair in the DNA sequence, which can lead to silent, missense, or nonsense mutations.

DNA Repair Mechanisms: DNA repair mechanisms are processes by which a cell identifies and corrects damage to its DNA molecules, helping to maintain genetic stability and prevent mutations.