Question

Frameshift mutations result from ________.

• A. \( \text{Recombination} \)
• B. \( \text{DNA methylation} \)
• C. \( \text{Base substitution} \)
• D. \( \text{Deletion or insertion of nucleotides} \)

Hint:

Think of a sentence: "THE CAT ATE RAT". If you delete "C", it becomes "THE ATA TER AT...", which makes no sense. This is a frameshift!

Answer 1

The Correct Option is D

Concept: The genetic code is read in groups of three nucleotides, called codons.
• The "reading frame" is the specific start point and sequence of these triplets.
• Maintaining this frame is essential for producing the correct protein sequence.

Step 1: The mechanics of a Frameshift.
A frameshift mutation occurs when nucleotides are either added (insertion) or removed (deletion) from the DNA sequence. If the number of nucleotides added or deleted is not a multiple of three, the entire downstream reading frame shifts.

Step 2: Consequences of the shift.
Every single codon after the mutation point will likely code for a different amino acid. This often results in a non-functional protein or the premature appearance of a "stop" codon. Base substitutions (Option C) usually only affect a single amino acid and do not cause a frameshift. Final Answer: Frameshift mutations are caused by the Deletion or insertion of nucleotides.