Question

Explain Frame shift mutation with an example.

Hint:

Insert or delete one base in a triplet-read sequence and see how every codon after it changes.

Answer 1

Step 1: Understanding the Concept:
A gene is read by the ribosome in groups of three bases at a time, called codons, starting from a fixed point. If bases are added or removed from the DNA in a number that is not a multiple of three, every codon downstream of that point shifts out of its normal grouping.

Step 2: Explain the mechanism.
This kind of mutation, caused by insertion or deletion of one or two nucleotides (or any number not divisible by three), is called a frame shift mutation, because it literally shifts the reading frame used to group bases into codons.

Step 3: Give an example.
Consider the sequence AUG-CAU-CAU-CAU, which normally codes methionine-histidine-histidine-histidine. If a single base A is inserted right after AUG, the sequence becomes AUG-ACA-UCA-UCA-U, so every codon after the insertion point reads differently, changing the entire amino acid sequence from that point onward.

Final Answer:
A frame shift mutation is an insertion or deletion not in multiples of three that shifts the reading frame and scrambles the protein sequence downstream of the mutation.