Mutation: Definition, Types, and Examples
Mutation Definition
Mutation originates from a Latin word which means change. Changes in the chromosome due alteration of a nucleotide sequence. This is called as Mutation. They can pass from one generation to another and are usually present forever within in an organism. Small scale mutations and large-scale mutations are the two types of mutations. Substitution, insertion and deletion type of mutation are small scale mutation. Those mutations which take place in a particular huge location are called as Large- scale mutation. Thus, leading to various deadlier disease.
Mutation Types
As discussed, prior, mutations can be of two types based on its effect and the structure:
i. Small-scale Mutation
Such types of mutation affects only a single nucleotides or few nucleotides. These can be further subclassified into; Substitution mutation, Deletion mutation and Insertion mutation. When a nucleotide is replaced with another nucleotide it is called as Substitution mutation. Example of substitution mutation are
• Pyrimidine replaced by purine(T-G)
• Purine replaced by another purine (A-G)
• Pyrimidine substituted by another pyrimidine (T-C)
• Purine replaced by pyrimidine (G-T)
The first and the last mutation are transversion type of mutation. The other two are transition types of mutation.
Point mutation is also referred to substitution mutation, when involves a single nucleotide or gene. There are various types of point mutation.
When there is shift in nucleotide bases due to addition or removal of nucleotides, it is called as Frame shift mutation, thus creating an issue while translating the mRNA into proteins.
In nonsense mutations, a protein is formed which is not complete and is very small. Example Cystic fibrosis.
Missense mutations occurs when, a single nucleotide is removed or added, thus leading to change in the base pair, thus from the amino acids a different protein would be formed than the required one.
A mutation with no positive and negative effect is called as neutral mutation.
A mutation in which no changes are seen in the amino acid, however, the protein functions is called as Silent mutation.
ii. Large-scale Mutation
They bring a change in the chromosome region, thus, they are called as large-scale mutation. They have several types such as deletion of chromosomal regions, inversion and gene duplication.
Causes of Mutation
The reason behind mutation to occur, when incorrect base pairs are inserted and, in their place, new nucleotides are added. This causes exposure to radiation such as chemicals, UV rays and other rays. For example, In, a DNA, when point mutation takes place, the mistake is rectified by reversing or by substituting it with other bases. Thus, when this error does not rectify or gets replaced it leads to mutation and may also get amplified, while replication of DNA.
Effect of Mutation
A new characteristics is created due to mutation; thus, they play a very important role as they bring out variations in population, nucleotide and etc. They may be beneficial as well as harmful. Inside the genes, is the DNA present which has genetic information along with the change. Thus, when they amino acid sequence in the polypeptide gets translated from mRNA to protein, the protein formed due to mutation will have various functions. However, few functions might get altered which could cause a disorder. An organism is said to be a mutant when it differs from its ancestors. The ancestors are called as the wild type. This mutation when passed further could get various new characteristic down the generation.
Mutation Examples
Animals such as a duck with four legs, cats with multiple legs, snakes with two head are examples of mutations, which could cause death after some time. Mutations are humans are due to genes getting altered. Example when the beta hemoglobin chain on nucleotide 20 of chromosome 11’s codon changes to GTG to GAG which produces valine rather than glutamic acid. Example of mutations in humans causing disorder are Turner syndrome, Klinefelter syndrome, Cystic fibrosis, Down syndrome, Cry du chat syndrome, Color blindness and Canavan are some of the example. Changes in the flowers, fruits, stem, foliage of a plant are the mutation examples seen in plants.
Mutation Citations
- Driven by Mutations: The Predictive Value of Mutation Subtype in EGFR-Mutated Non-Small Cell Lung Cancer. J Thorac Oncol . 2017 Apr;12(4):612-623.
- Somatic mutation in cancer and normal cells. Science . 2015 Sep 25;349(6255):1483-9.
- Mechanisms of viral mutation. Cell Mol Life Sci . 2016 Dec;73(23):4433-4448.
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