Frameshift mutation is defined as a mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide. Which option best represents this definition?

Frameshift mutation is defined as a mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide. Which option best represents this definition?

• A. Mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide
• B. Mutation that changes a single base
• C. Mutation that adds a base pair
• D. Mutation that duplicates a segment

Answer: (A)

Frameshift mutations change how the genetic code is read because the code is read in groups of three nucleotides (codons). If you insert or delete a single nucleotide, the grouping of all downstream codons is shifted, so every codon from that point on codes for a different amino acid, often producing a nonfunctional protein or a premature stop signal. The option that states insertion or deletion of a nucleotide directly captures this mechanism, making it the best representation. Other choices describe different mutation types—changing a single base is a point mutation, adding two nucleotides (a base pair) changes the sequence differently, and duplicating a segment doesn't shift the reading frame—so they don’t describe a frameshift as accurately.

Frameshift mutations change how the genetic code is read because the code is read in groups of three nucleotides (codons). If you insert or delete a single nucleotide, the grouping of all downstream codons is shifted, so every codon from that point on codes for a different amino acid, often producing a nonfunctional protein or a premature stop signal. The option that states insertion or deletion of a nucleotide directly captures this mechanism, making it the best representation. Other choices describe different mutation types—changing a single base is a point mutation, adding two nucleotides (a base pair) changes the sequence differently, and duplicating a segment doesn't shift the reading frame—so they don’t describe a frameshift as accurately.