A genetic mutation is a permanent change in the nucleotide sequence of an organism's genome. Mutations can arise from unrepaired DNA or RNA damage, replication errors, or mobile genetic elements. They play a role in both normal and abnormal biological processes like evolution, cancer development, and the immune system. There are two main types of mutations: somatic mutations, which occur in non-reproductive cells and are not inherited, and germline mutations, which occur in reproductive cells and can be passed to offspring. Mutations can be classified in several ways based on their structure, function, protein effects, and inheritance patterns. They can arise spontaneously from DNA damage or errors, or be induced by chemicals, radiation, and other mutagens

1. Genetic Mutation
A Permanent Change in the
Nucleotide Sequence of
the Genome of an Organism

2. Genetic Mutation:
In genetics, a mutation is a change of the nucleotide sequence of
the genome of an organism, virus, or extra chromosomal genetic
element.
Mutations result from unrepaired damage to DNA or to RNA
genomes, errors in the process of replication, or from the insertion
or deletion of segments of DNA by mobile genetic elements.
Mutations play a part in both normal and abnormal biological
processes including: evolution, cancer, and the development of the
immune system.

3. Somatic Mutation:
Acquired Mutation:
A change in the genetic structure that is not inherited from
a parent, and also not passed to offspring
Not present in the germ-line of the organism
Will change the phenotype of the individual containing it
If occurs early during organismal development, will likely
be in many cells, seeming as though the mutation exists in
the entire organism
If occurs later during organismal development, may only
be in a few cells within the organism.

4. Germinal Mutation:
Germline Mutation:
Any detectable and heritable variation in the lineage of germ
cells.
Exists or has occurred in the sperm or egg and is passed to the
progeny.
Can occur during early embryonic development when the
embryo is made up of only a few cells.
Would be present in almost all of the resulting organism's cells.

5. Classification of Mutation Types:
By Effect on Structure:
Point mutations, often caused by chemicals or malfunction of DNA replication,
exchange a single nucleotide for another (e.g., conversion of adenine [A] into
a cytosine [C]).
Insertions, add one or more extra nucleotides into the DNA. They are usually
caused by transposable elements, or errors during replication of repeating
elements (e.g., AT repeats).
Deletions, remove one or more nucleotides from the DNA. In general, they are
irreversible.
Amplifications(or gene duplications), leading to multiple copies of all
chromosomal regions, increasing the dosage of the genes located within them.
Loss of heterozygosity: loss of one allele, either by a deletion or
a recombination event, in an organism that previously had two different alleles.

7. By Effect on Function:
Amorphic mutation, result in the gene product having less or no function. When
the allele has a complete loss of function (null allele) it is often called an Loss-of-
function mutations.
Aneomorphic mutation, change the gene product such that it gains a new and
abnormal function. These mutations usually have dominant phenotypes. Often
called Gain-of-function mutations.
Antimorphic mutations, have an altered gene product that acts antagonistically
to the wild-type allele. These mutations usually result in an altered molecular
function (often inactive) and are characterized by a dominant or semi-dominant
phenotype, also called as Dominant negative mutations. In humans,
dominant negative mutations have been implicated in cancer
Lethal mutations, are mutations that lead to the death of the organisms that
carry the mutations.
A back mutation or reversion is a point mutation that restores the original
sequence and hence the original phenotype

8. By Impact on Protein Sequence:
Frameshift mutation, is a mutation caused by insertion or deletion of a number of
nucleotides that is not evenly divisible by three from a DNA sequence.
Non-sense mutation, is a point mutation in a sequence of DNA that results in a
premature stop codon, or a nonsense codon in the transcribed mRNA, and often non-functional
protein product.
Missense mutations or non-synonymous mutations, are types of point
mutations where a single nucleotide is changed to cause substitution of a different
amino acid. Such mutations are responsible for diseases such as sickle-cell disease.
Neutral mutation, is a mutation that occurs in an amino acid codon that results in the
use of a different, but chemically similar, amino acid. The similarity between the two
is enough that little or no change is often rendered in the protein. e.g., a change from
AAA to AGA will encode arginine, a chemically similar molecule to the
intendedlysine.
Silent mutations, are mutations that do not result in a change to the amino acid
sequence of a protein, unless the changed amino acid is sufficiently similar to the
original. They may occur in a region that does not code for a protein

9. By Inheritance:
A heterozygous mutation is a
mutation of only one allele.
A homozygous mutation is an
identical mutation of both the
paternal and maternal alleles.
Compound
heterozygous mutations or
a genetic compound comprises
two different mutations in the
paternal and maternal alleles.
A mutation has caused this gardenmoss rose to
produce flowers of different colors. This is a somatic
mutation that may also be passed on in the germ line.

10. Causes of Mutation:
Spontaneous Mutation
Spontaneous mutations on the molecular level can be caused by:
 Tautomerism — A base is changed by the repositioning of a hydrogen atom,
altering the hydrogen bonding pattern of that base, resulting in incorrect
base pairing during replication.
 Depurination — Loss of a purine base (A or G) to form an apurinic site.
 Deamination — Hydrolysis changes a normal base to an atypical base
containing a keto-group in place of the original amine group. Examples
include C → U, which can be corrected by DNA repair mechanisms.
 Slipped strand mispairing — Denaturation of the new strand from the
template during replication, followed by renaturation in a different spot. This
can lead to insertions or deletions.

11. Error Prone Replication By-Pass:
Majority of spontaneously arising mutations are due to error
prone replication past a DNA damage in the template strand.
Naturally occurring DNA damages arise about 60,000 to
100,000 times per day per mammalian cell.

12. Errors Introduced During DNA Repair:
A Non-homologous end joining is
a major pathway for repairing
double-strand of DNA breaks.
NHEJ involves removal of a few
nucleotides to allow inaccurate
rejoining of the two ends.
It followed by addition of
nucleotides to fill in gaps.
As a result, NHEJ often
introduces mutations.

13. Induced Mutation:
Induced mutations on the molecular level can be caused by:-
Chemicals
 DNA intercalating agents (e.g., ethidium bromide)
 DNA cross linkers
 Oxidative damage
 Base analogs (e.g., BrdU) etc.
Radiation
 Two nucleotide bases in DNA (cytosine and thymine) are most sensitive to
ultraviolet radiation that can change their properties.
 Ultraviolet radiation, in particular longer-wave UVA, can also
cause oxidative damage to DNA.

14. Mutation and Cancer:
Cancer tumors are a unique class of somatic mutations.
Cancer results when cells accumulate genetic errors and multiply
without control.
The tumor arises when a gene involved in cell division is mutated.
All of the daughter cells contain this mutation.
The phenotype of all cells containing the mutation is uncontrolled
cell division. This results in a collection of undifferentiated cells
called Cancer cells.
Usually, it takes multiple mutations over a lifetime to cause cancer.

15. Examples of Cancer in Plants: