Question

Explain Frameshift mutation?

Answer 1

A frameshift mutation is a genetic mutation caused by indels of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame, resulting in a completely different translation from the original

Answer 2

Answer:

Codons are three consecutive bases which are recognized by the ribosome as coding for a particular amino acid (it can get more complex, but this is the basic truth with all known natural DNA and RNA organisms). The codons for a particular protein are always immediately adjacent to each other (again, excepting some complex variations), and are inframe (a multiple of 3 away) from the MET start codon of the protein.

If bases are added or subtracted within an Open Reading Frame (ORF), aka Coding Sequence (CDS), aka a few other terms, suddenly the codons which include those additions and subtractions are changed. Often the downstream codons are also changed, if the addition or subtraction isn’t a multiple of three, or includes an inframe stop codon. If the additions or subtractions are not a multiple of three, then this is called a frameshift mutation.

It is called a frameshift mutation because the codon “reading frame” - every three bases - has been shifted relative to the bases which are downstream of the shift.

The consequences of these mutations are that you get a new protein, the beginning of which (before the frameshift) is identical in composition to the original protein, but the end of which (after the frameshift) is different. It may be longer than the original, shorter than the original, it may create a fusion of two proteins, but whatever happens, unless the frameshift is very near the end of the protein, or a subsequent frameshift very close to the first frameshift corrects the issue, you get a protein that isn’t doing what it’s expected to do. The effects of this will vary from the unnoticed to cell death.

Examples of frameshifts (deletion and insertion frameshifts, respectively):