Question

Acridine dyes induce frameshift mutations. Why are frameshift mutations likely to be more detrimental than point mutations, in which a single pyrimidine or purine has been substituted?

Short answer

Answer: Frameshift mutations are generally more detrimental than point mutations because they cause a shift in the reading frame of the gene, affecting all downstream codons. This often leads to the production of a completely different, non-functional protein with altered amino acid sequences and possibly premature stop codons, compared to point mutations, which have a more localized effect and can sometimes be silent or have minor consequences on protein function.

Step-by-step solution

Define frameshift and point mutations

A frameshift mutation occurs when a nucleotide is added or deleted, causing a shift in the reading frame of the gene. A point mutation, on the other hand, is the substitution of one nucleotide by another, which may or may not result in a change in the amino acid sequence of the corresponding protein.

Effects of point mutations

Point mutations can result in various outcomes: 1. Silent mutation: If the substitution does not change the encoded amino acid (due to the degeneracy of the genetic code), it is called a silent mutation. Silent mutations typically have no effect on protein function. 2. Missense mutation: If the substitution leads to a different amino acid being incorporated, it is called a missense mutation. Missense mutations can have varying effects on protein function, depending on the properties of the new amino acid and its importance in the protein's structure and function. 3. Nonsense mutation: If the substitution creates a premature stop codon, it is called a nonsense mutation. This typically leads to a non-functional, truncated protein.

Effects of frameshift mutations

Frameshift mutations result from insertions or deletions of nucleotides, causing a shift in the reading frame. This, in turn, affects all downstream codons of the mutated gene. In most cases, this leads to the production of a completely different, non-functional protein with altered amino acid sequences. Moreover, if a premature stop codon is encountered due to the frameshift, the protein will be truncated and likely non-functional.

Comparing frameshift and point mutations

As seen above, frameshift mutations often lead to the production of non-functional proteins due to a large-scale change in amino acid sequences, whereas point mutations have a more localized effect and can sometimes be silent or have minor consequences on protein function. Hence, frameshift mutations are generally more detrimental than point mutations because they impact a larger portion of the gene and potentially disrupt the overall structure and function of the protein.