[Campbell Biology P.39] A single nucleotide deletion occurs near the beginning of the codin... | Practice Question

A single nucleotide deletion occurs near the beginning of the coding sequence of a gene. What is the most likely consequence of this mutation on the resulting polypeptide?

  • A: It will likely result in a silent mutation, leading to no change in the amino acid sequence.
  • B: It will cause a missense mutation, changing only a single amino acid in the polypeptide.
  • C: It will lead to a frameshift mutation, drastically altering the amino acid sequence downstream and likely resulting in a nonfunctional protein.
  • D: It will introduce a premature stop codon, shortening the polypeptide, but only if the deletion occurs at the very end of the gene.

Explanation

A single nucleotide deletion within the coding sequence, especially near the beginning, causes a frameshift mutation. This shifts the reading frame for all subsequent codons, leading to a completely altered amino acid sequence downstream from the deletion, and often results in a premature stop codon, producing a truncated and usually nonfunctional protein.