AAT Bioquest

What are the classifications of structural chromosomal mutations?

Posted January 16, 2023


There are several classifications of structural chromosomal mutations based on the type of change that occurs. The main classifications include:  

Translocation: This type of structural mutation is caused when part of a chromosome detaches and transfers to a new position on a non-homologous chromosome. In translocation, the chromosomes are simply rearranged - there is no net gain or loss of chromosomes. 

Inversion: In inversion, part of a chromosome breaks and rotates by 180 degrees on its own axis. The reversed segment is then inserted back into the chromosome. The sequence is simply rearranged in this type of mutation – there is no loss or gain of chromosomes. Chromosomal inversion occurs only in larger species and acts as an evolutionary asset, boosting the fitness of the species. Smaller species would not be able to survive an inversion mutation. 

Duplication: Duplications are caused when a chromosome generates extra copies of genes. The duplicated region may be present in close proximity to the normal section (tandem duplication) or it may be located at a distance (displaced duplication). In reverse tandem duplication, the sequence of genes in the duplicated region is the reverse of the normal sequence. 

Deletion: Deletion mutations are caused when a chromosome breaks and part of the chromosome gets lost during cell division. The genetic material can break off from anywhere on the chromosome. Deletion mutations are permanent. A chromosome that has undergone deletion cannot revert back to normal and can be hereditary if transmitted to the next generation.

Isochromosome: Isochromosomes are a type of chromosome mutation caused by the improper division of the centromere. A typical chromosome has one long and one short arm, whereas an isochromosome may have both long or both short arms.

Additional resources

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