21. Which of the statements best describes the mutational event pictured below? Wild-type sequence ACC CAC UCU GGA UUU AAG GCA Peptideencoded thr his ser gly leu lys ala Mutant sequence ACC CAC UCU UGA UUU AAG GCA Peptideencoded thr his ser stop phe lys ala (A) A transversion mutation leading to a nonsense codon (B) A frameshift mutation leading to a missense amino acid substitution (C) A transition mutation resulting in a silent amino acid substitution (D) A transition mutation leading to a nonsense codon (E) An insertion mutation resulting in a frameshift of the amino acid sequence