What are the different types of chromosomal mutation?

Chromosomes are long thread-like structures of DNA that contain all or part of an organism’s genetic material. Chromosomal mutations occur when the structure or number of chromosomes in a cell is altered. Chromosomal mutations may be categorized as Chromosomal Mutations I or Chromosomal mutations II. 

Chromosomal mutations I

These involve mutations that change the structure of the chromosome. These are further divided into 4 types based on the mechanism of the mutation: 

1. Inversion chromosomal mutation: In an inversion mutation, a chromosome segment that is removed rotates by 180° on its own axis before getting reattached to the chromosome but in the opposite direction than it was originally. No genes are gained or lost in an inversion mutation. The sequence is simply rearranged. 
2. Deletion chromosomal mutation: A deletion mutation occurs when a chromosome segment gets removed or deleted. In a terminal deletion, only one piece at the end of the chromosome is deleted. In an interstitial deletion, two pieces of chromosome are deleted – one at the end and one within the chromosome. In a deletion mutation, a portion of a chromosome is permanently lost. 
3. Duplication/Amplification chromosomal mutation: This is a type of chromosomal mutation in which an extra copy of a segment or the entire chromosome is present in the nucleus. The duplication can occur anywhere along the chromosome including the ends. 
4. Translocation chromosomal mutation: A translocation mutation occurs when a segment of a chromosome breaks off and transfers or relocates to a completely different (nonhomologous) chromosome, creating a fusion chromosome. In this type of mutation, no chromosomes or genes are gained or lost. They are only rearranged. 

Chromosomal Mutations II

These involve mutations that change the number of chromosomes in the cell. These are further divided into 2 types: 

1. Aneuploidy: This type of chromosomal mutation alters parts of a chromosome set, causing either the addition or loss of one or more chromosomes. 
2. Polyploidy: In this type of chromosomal mutation, two sets of genomes are created within an organism. It is not naturally common and is only observed in some plants, where it causes effects such as reduced fertility or gigantism.