Mutation and Its types

Mutation 

Mutation is defined in simply words as "Stable Genetic alteration" occurs due to change in the nucleotide sequences of a short region of a genome, caused by either error during DNA replication or by the damaging effects of mutagens such chemical and radiation. 

Chemical Mutagens are Reactive oxygen species, nitrous acid, ethidium bromide,sodium azide etc. 

Radiations are ultraviolet, gamma rays, X-rays etc. 

List of Mutation types and their examples. 

Mutation type	Definition	Example	Notes
Transitions	base pair substitution (purine to another purine and pyrimidine to another pyrimidine )	A --> G or G --> A (Purine), C --> T or T --> C (Pyrimidine)
Transversion	base pair substitution (purine to pyrimidine or pyrimidine to purine)	A --> C or C --> A, G --> T or T --> G
Frame shift	Indels of number of nucleotides in a DNA sequence (not divisible by three) can change the reading frame resulting in a different translational.	Original mRNA sequence: 5′ GTC GTT TTA CAA 3′ --> functional protein.                                                                        Frame shift mutation sequence : GTC GTT T TTA CAA or GTC GTT C TTA CAA	Indels means insertion or deletion in molecular biology.
Point	Single nucleotide is replace by a different nucleotide	examples similar to transition and transversion mutation	It’s a type of base substitution mutation.
Silent	mutation is a result of substitution occurring at the third position of the codon, but it has no effect in the protein activity	GAA is mutated to GAG, but both the codons code for small amino acid i.e. glutamate.	It’s a type of point mutation.
Missense	This results in change in protein activity, since the substitution of nucleotide in the codon codes for a different amino acid.	CAT which codes for histidine are changed to CCT that code for proline.	It’s a type of point mutation.
Nonsense	The mutation is similar to Missense expect that the resulting codon will be a STOP codon.	CAG --> TAG i.e. Glutamine to STOP codon.	It’s a type of point mutation.
Deamination	Conversion of a primary amino group to a ketone.	Deamination of cytosine to uracil results in a base substitution.	ung gene product in E.Coli is an enzyme that specifically removes uracil from DNA.
Base analogs	A compound similar to that of the nitrogenous base is incorporated in the growing polynucleotide chain during replication. It causes a stable mutation.	5-Bromouracil is an analog for Thymine.  So, AT --> A5BU. Now during replication, Since 5BU is ionized, its complementary binds to G rather than A. So A5BU results in AT and G5BU. Now during next replication, G5BU is again gives rise to G5BU and GC.	It’s a stable mutation and also it only can be induced artificially.
Leaky mutation	Amino acid substitution mutation causes only partial disruption of the protein function.	A mutation makes the bacteria not to survive in a particular medium, But the bacteria has a leaky mutation at the mutation site, then it slowly grow on the restricted media.
Transposition mutation	Insertion of transposons at the site causes this mutation.	It basically gives rise to antibiotic resistance and most Multi antibiotic resistant bacteria have this mutation.