[Campbell Biology P.411] What is the most likely consequence if a single nucleotide pair is ... | Practice Question

What is the most likely consequence if a single nucleotide pair is lost from the middle of the coding sequence of a gene?

  • A: A silent mutation, resulting in no change to the amino acid sequence.
  • B: A missense mutation, changing only one amino acid in the resulting polypeptide.
  • C: A frameshift mutation, leading to extensive changes in the amino acid sequence downstream and potentially a premature stop codon.
  • D: A nonsense mutation, immediately causing a premature stop codon without any preceding amino acid changes.

Explanation

The passage highlights the importance of the 'correct reading frame' for codons. Losing a single nucleotide pair from the middle of a coding sequence would cause a frameshift mutation, where all subsequent codons are read incorrectly. This typically leads to a drastically altered amino acid sequence and often results in a premature stop codon, producing a truncated, non-functional protein.