Frameshift mutation

Definition

A frameshift mutation is a genetic alteration caused by the addition or deletion of nucleotides in a DNA sequence, which shifts the reading frame of the genetic code. This shift can lead to the production of completely different and often nonfunctional proteins. Understanding frameshift mutations is crucial as they can occur through various mechanisms and have significant implications for the central dogma of molecular biology, which describes how genetic information flows from DNA to RNA to proteins.

5 Must Know Facts For Your Next Test

1. Frameshift mutations can occur due to insertions or deletions of one or more nucleotides in a DNA sequence, but they only affect the reading frame if the number of nucleotides added or removed is not a multiple of three.
2. These mutations often result in proteins that are truncated or contain many incorrect amino acids, potentially leading to severe biological consequences such as diseases.
3. Frameshift mutations are more likely to cause harmful effects than point mutations due to the extensive alteration of the resulting protein structure.
4. Certain mutagens, like chemical agents or radiation, can increase the rate of frameshift mutations by damaging DNA and leading to insertion or deletion events.
5. Frameshift mutations play an essential role in evolutionary processes by introducing variability in proteins, which can be subject to natural selection.

Review Questions

• How does a frameshift mutation differ from a point mutation in terms of its impact on protein synthesis?
  • A frameshift mutation differs from a point mutation primarily because it alters the entire reading frame of the genetic code, potentially affecting all downstream codons and resulting in a completely different protein. In contrast, a point mutation only changes a single nucleotide and may only affect one codon, often leading to less drastic changes in protein function. This difference means that frameshift mutations generally have more severe consequences for protein synthesis than point mutations.
• Describe the mechanisms through which mutagens can induce frameshift mutations and provide examples.
  • Mutagens can induce frameshift mutations through various mechanisms, such as intercalating agents that insert themselves between DNA bases or through chemicals that cause the addition or deletion of nucleotides. For example, certain chemicals like acridine orange can slip between base pairs, causing insertions during DNA replication. Additionally, radiation can damage DNA strands, leading to deletions when repair mechanisms attempt to fix these breaks incorrectly. These interactions highlight how mutagens can disrupt normal genetic processes and lead to significant alterations in gene expression.
• Evaluate the implications of frameshift mutations on evolutionary biology and how they contribute to genetic diversity.
  • Frameshift mutations play a critical role in evolutionary biology by generating genetic diversity that can be acted upon by natural selection. While many frameshift mutations are deleterious and can lead to diseases, some may confer advantageous traits under specific environmental conditions. This variability allows populations to adapt over time, as beneficial frameshifts may enhance survival and reproduction. Thus, despite their potential negative impacts, frameshift mutations contribute significantly to the dynamic process of evolution by introducing new variations into the gene pool.

Related terms

Point mutation: A point mutation is a change in a single nucleotide in a DNA sequence, which can result in a different amino acid or no change at all, depending on the context.

Mutagen: A mutagen is an agent that causes changes in DNA, leading to mutations, including frameshift mutations, through various mechanisms.

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