What Is The Molecular Basis Of Mutation?

Mutations in the genes can be induced or could arise spontaneously. Induced mutations are generated when an entity is exposed to a mutagen or an agent causing mutations. These mutations usually tend to have higher frequencies than spontaneous mutations. Spontaneous mutations are the naturally occurring mutations which appear in all cells. Comprehension of the gene mutation mechanism requires DNA analysis and also the analysis of protein molecules.

Also Read: Mutation – A Genetic Change

What is a Gene Mutation?

A gene mutation can be described as a change or alteration in the sequence of nucleotides in a DNA polymer which is a series of nucleotides joined together. It can be altered in many ways and can have effects on the health of an individual. It can cause genetic disorders depending upon the site at which they occur and whether they can alter functions of essential proteins. While some other mutations could be beneficial, making individuals better adapt to their surroundings.

Types of Mutations

Substitution Mutation

It is a mutation that switches a single chemical letter or base for another. It places the wrong nucleotide in the wrong position. It could result in a silent mutation. In such a mutation, a codon is altered to another that encodes the corresponding amino acid resulting in no change in the protein that is generated or it could alter an amino-acid coding codon to a single-halt codon resulting in the formation of an incomplete protein which could be non-functional. Also, it could cause an alteration in a codon to one that encodes another amino acid causing a small change in the protein synthesized.


It causes an alteration in the number of DNA bases in a gene by inserting a piece of DNA. Consequently, the protein produced may not be functional.

See Also: Genes


A change in the number of bases of DNA is caused due to the deletion of a piece of DNA. Any number of nucleotides can be deleted or removed. Small deletions may cause the dismissal of a few base pairs within a gene, while larger deletions can discard a whole gene or neighbouring genes producing an alteration in the functions of resulting proteins.

Frameshift Mutation

It occurs when a deletion or addition of DNA bases causes an alteration in the reading frame of a gene. There are three groups of base pairs wherein each code for one amino acid in a reading frame. This type of mutation causes a shift in the organization of these bases and modifies the code for amino acids. Consequently, it results in non-functional proteins. Duplications, deletions and insertions could all be frameshift mutations. Visit BYJU’S to explore more about gene mutations in humans and related topics.

A careful study of DNA models, protein structures can lead to a better understanding of the nature of mutations and the causative for alterations of these structures. Sequences of large segments of DNA can be determined using molecular genetic techniques. Changes in these sequences cause mutations. The concept of sequencing has made it much easier to understand the track that drives to mutagenesis. It has also aided to interpret the mutational hot spots which are the genetic sites with an inclination towards mutating.

Research has been carried out on single-celled bacteria and their viruses to examine the molecular basis of mutation. Inherited diseases caused by mutations in humans are also explored to understand the concept better. Another related mechanism which plays a key role in mutagenesis is the biological repair mechanism which operates to reduce the ultimately observed mutation rates. For instance, in the E-Coli, with all its repair systems operating well, the base substitutions take place at rates of per base pair per cell per generation.

The base substitutions occur through a disturbance of the normal pairing of corresponding bases as part of the basic principle.

Also Read: Mutagens

For more information on mutation, its types, gene mutation and related topics,  visit us at BYJU’S Biology.


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