Types of Mutations: Definition, Structure, Expression, Facts, Characteristics, Functions

What Is Mutation?

A mutation is generally defined as any permanent change in the DNA sequence coding for a gene. This can imply a change in the sequence of just a single DNA building block—a nucleotide—or several nucleotide pairs being added to or removed from the DNA molecule. It describes large-scale chromosomal changes at the level of genes, including gene duplications and deletions, and chromosomal rearrangements. These can also modulate effects that are benign or severe on an organism, according to its nature and location.

Latest: NEET 2024 Paper Analysis and Answer Key 

Don't Miss: Most scoring concepts for NEET | NEET papers with solutions

New: NEET Syllabus 2025 for Physics, Chemistry, Biology

NEET Important PYQ & Solutions: Physics | Chemistry | Biology | NEET PYQ's (2015-24)

This Story also Contains

1. What Is Mutation?
2. Mechanisms
3. Classification Of Mutations
4. Types Of Mutations
5. The Video Recommended On Types Of Mutations:

Mechanisms

The mechanisms of genetic diversity and evolution can be understood only by studying mutations. Indeed, mutations are the base of evolution because they provide the required genetic variability on which natural selection works. In addition, a great proportion of mutations lead to different types of genetic disorders and cancers. Therefore, studies on these mutations are greatly relevant to medical research on treatment. By understanding how these mutants occur and their consequences, scientists come up with ways to prevent and treat these genetic diseases.

How DNA mutations can be classified are many and varied. These are based on the point of origin of the mutation, its effect on a given organism, which relates to its standpoint, and the type of cells affected. These range from point mutations to insertions/deletions, chromosomal mutations, all the way to copy number variations.

Classification Of Mutations

Mutations can be categorised based on their origin and also by the type of cells they affect.

Based On Origin

Spontaneous Mutations: These occur naturally, independent of any exogenous influence. Evidence is found in errors in processes like DNA replication or its repair. Although spontaneous mutation is relatively a rare event, it still can add up through time and so may lead to increased genetic diversity and evolution.

Induced Mutations: Due to external factors such as radiation, chemicals, or viruses, such mutations make up the bulk of induced mutations. In comparison with spontaneous mutation rates, induced mutations are more common and can be used in a laboratory setting to investigate gene function and regulation.

Based On Cell Type

Germline Mutation: This involves mutation in the reproductive cells; that is, the sperm and egg, hence transmissible to offspring. Germline mutations are important for the process of evolution because they lead to an increase in genetic variation within populations. They are also responsible for inherited genetic disorders.

Somatic Mutations: These are the mutations that occur in non-reproductive cells. Since they don't happen in the reproduction cells, they are not passed down to offspring. Somatic mutations can cause cancer and other diseases because they can make the cells grow and reproduce uncontrollably.

Types Of Mutations

The types of mutations are:

Point Mutations

Point mutations are changes in a single nucleotide pair of gene structure. They can have various effects depending on the nature of the substitution and its location in the gene.

Types:

Silent Mutations

These are mutations that do not alter the amino acid sequence of the protein due to redundancy in the genetic code.

Missense Mutations

The result of these mutations is the substitution of one amino acid for another in the protein; this may frequently alter the function of the protein.

Nonsense Mutations

In such mutations, a codon for an amino acid is changed into a termination or stop codon, which results in the truncation of a normally functioning protein.

Examples and Effects: Point mutations can result in sickle cell anaemia, which is a missense mutation, and cystic fibrosis, which is caused by a nonsense mutation.

Insertions And Deletions (Indels)

Insertions and deletions refer to the addition or removal of one pair or more of nucleotides in the DNA.

Frameshift Mutations

InDels not in multiples of three nucleotides lead to a changed reading frame of the message and changes in the amino acid sequence massively downstream of the mutation.

Examples and Effects: Frameshift mutations can result in serious genetic disorders like Tay-Sachs disease, wherein its deletion causes a non-functional enzyme.

Chromosomal Mutations

Chromosomal mutations are larger in scale and have different structures of chromosomes, which can bring prominent effects on an organism.

Types

• Deletions

A segment of a chromosome may get lost, and therefore, all genes contained in that segment are also lost.

• Duplications

A segment in a chromosome may be duplicated and inserted into an organism's genome, yielding multiple copies of the same gene.

• Inversions

A segment of a chromosome is inverted end to end.

• Translocations

A deletion of a segment of one chromosome and its attachment to another chromosome.

Examples and Effects: Chromosomal mutations lead to developmental disorders and cancers. An example is chronic myeloid leukaemia, which often results from a reciprocal translocation between chromosomes 9 and 22.

Copy Number Variations CNVs

The copy number variations are altered copies of any particular gene or, in general, of any genomic region.

Examples and Effects: CNVs can lead to increased genetic variation within populations and have been implicated in diseases like autism and schizophrenia, where altered numbers of gene copies may influence brain development and function.

Conclusion

Mutations are changes in the DNA sequence that hold the potential to affect an organism in various intensity strengths. More broadly, they can be categorised by their origin and by the type of cells affected. The major types of mutations include point mutations, insertions and deletions, chromosomal mutations, and copy number variations, all of which have different characteristics and consequences. Knowing mutations is needed for studies on genetic diversity, evolutionary processes, and mechanisms underlying human diseases. The future of mutation biology holds the key to new treatments for genetic disorders and deepens our understanding of evolutionary processes.

The Video Recommended On Types Of Mutations: