Frameshift Mutation in mRNA Translation

Steps:

• mRNA is translated into protein by reading codons, each three nucleotides long.
• Deleting one nucleotide shifts the reading frame from the deletion point onward.
• This alters all subsequent codons, changing the amino acid sequence.
• The resulting protein has a different primary structure after the mutation site.

Why D is correct:

• The genetic code is read in non-overlapping triplets; a single nucleotide deletion causes a frameshift, altering all downstream codons per the central dogma of molecular biology.

Why the others are wrong:

• A: Frameshift changes multiple amino acids, not just a synonymous codon substitution.
• B: Frameshift affects many amino acids, disrupting tertiary structure beyond one change.
• C: Frameshift alters the entire sequence after deletion, not just one amino acid; quaternary structure is unrelated.

Final answer: D