Mutation | Definition, Type, Missense mutation, Nonsense mutation

Hello friends, today we are going to study a very important topic, namely, what is mutation? Friend, you must have seen one or the other movie with mutation. Friends, in this we will study mutation thoroughly step by step, so let’s start.

What is mutation?

Definition of Mutation –

A sudden change in the genotype and phenotype of an organism is called a mutation.

Changes in the DNA/nucleotide sequence of the somatic cell as well as the gamete cell. It is called a mutation.

What is Variation?

When mutation and recombination occur together, a new species is formed, then it is called speciation, and when a new form of the organism is formed by this action, then it is called transformation.

How many types of mutations?

There are three types of mutations.

1. Genetic Mutation
2. Gene Mutation
3. Chromosomal Aberrations

What is Genetic Mutation?

When there is a change in the number of chromosomes of an organism, it is called a genetic mutation.

It is of two types.

1. Aneuploidy
2. Euploidy/Polyploidy

Aneuploidy –

There is a change in the number of chromosomes. If chromosome segregation or segregation fails during cell division.

Euploidy/Polyploidy –

It is commonly found in plants. In this, there is a change in the entire set or collection of chromosomes if cytokinesis (a division of the cytoplasm) fails after telophase.

What is Gene Mutation?

Any change in the structure, configuration, or number of genes is called gene mutation. A gene mutation can be of two types.

1. Frameshift
2. Replacement

Frameshift –

Such a change in the structure of a gene, due to which its entire gene structure changes is called a frameshift mutation.

It is of the following three types.

1. Deletion
2. Addition
3. Substitution

Deletion –

In this, the change in gene structure is due to the decrease in nucleotides.

Addition –

In this, the change in gene structure is due to the increase in the number of nuclease tides.

Substitution –

In this, the number of genes remains unaffected rather the nucleotide is exchanged between them.

It is of the following two types.

1. Transition
2. Transversion

Transition –

In this, the exchange takes place between similar nuclei.

For example, purine is exchanged with purine and pyrimidine with a pyrimidine.

Transversion –

In this, the exchange takes place between unequal nuclei, that is, the exchange of purine with pyrimidine and its substitution mutation can be of the following three types in addition to the above.

1- Silent Mutation –

In this, the codon is changed but the changed codon codes for the same amino acid.

2. Missense Mutation –

In this, the codon is changed in such a way that the changed codon codes for a different amino acid.

3. Nonsense Mutation –

In this, the normal codon is converted into a nonsense codon.

Chromosomal Aberrations –

When there is a change in the structure of the chromosome of an organism, it is called a Chromosomal Aberration, in which two changes are involved.

Out of which there is a change in the arrangement of genes present in the first chromosome or there is a change in its number. It is also called Structural Aberrations.

It mainly occurs during the reduction division.

Due to chromosomal abnormality –

The chromosomal abnormality is caused by the breakage of the chromosome and the rejoining of the broken fragment in the abnormality. Chromosome breakage can be induced by radiation (X-rays, gamma rays), chemical mutagenic agents such as insecticides, herbicides, alkali analogs, and various viruses. Chromosome breaks are also induced in some genes.

Structural Changes in Chromosomes –

It is of two types.

1. Change in The Number of Genes
2. Change in the Arrangement of Genes

Change in the Number of Genes –

In this, there are changes in the number of genes.

Deletion – In this, one or more genes decrease due to the breakage of chromosomes, and only the broken part decreases in it.

Duplication – It is the addition of one or more genes, as a result of which the organism bears duplicated genes in its haploid chromosome complement.

Change in the Arrangement of Genes –

In this, there is a change in the systematic form of the gene.

Translocation – It is the exchange of parts between non-homologous chromosomes to form new chromosomes.

Inversion – This involves the rotation of a block of genes within a chromosome by 180 degrees.

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