Gene Mutation- Bio

A gene is essentially a sentence made up of the bases A, T, G, and C that describes how to make a protein. Any changes to those instructions can alter the gene's meaning and change the protein that is made, or how or when a cell makes that protein. There are many different ways to alter a gene, just as there are many different ways to introduce typos into a sentence. In the following examples of some types of mutations, we use the sentence "The fat cat ate the wee rat" as a sample gene:
Point Mutation
A point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence, such as this example, where we change the 'c' in cat to an 'h':


Original
The fat cat ate the wee rat.

Point Mutation The fat hat ate the wee rat.

Frame-shift mutation
Frame-shift mutations. In a frame shift mutation, one or more bases are inserted or deleted, the equivalent of adding or removing letters in a sentence. But because our cells read DNA in three letter "words", adding or removing one letter changes each subsequent word. This type of mutation can make the DNA meaningless and often results in a shortened protein. An example of a frame-shift mutation using our sample sentence is when the 't' from cat is removed, but we keep the original letter spacing:


Original
The fat cat ate the wee rat.

Frame Shift The fat caa tet hew eer at.

Deletion
Mutations that result in missing DNA are called deletions. These can be small, such as the removal of just one "word," or longer deletions that affect a large number of genes on the chromosome. Deletions can also cause frameshift mutations. In this example, the deletion eliminated the word cat.


Original
The fat cat ate the wee rat.

Deletion The fat ate the wee rat.

Insertion
Mutations that result in the addition of extra DNA are called insertions. Insertions can also cause frameshift mutations, and general result in a nonfunctional protein.


Original
The fat cat ate the wee rat.

Insertion The fat cat xlw ate the wee rat.

Inversion
In an inversion mutation, an entire section of DNA is reversed. A small inversion may involve only a few bases within a gene, while longer inversions involve large regions of a chromosome containing several genes.


Original
The fat cat ate the wee rat.
Insertion The fat tar eew eht eta tac.


DNA expression mutation
There are many types of mutations that change not the protein itself but where and how much of a protein is made. These types of changes in DNA can result in proteins being made at the wrong time or in the wrong cell type. Changes can also occur that result in too much or too little of the protein being made