What are the types of chromosomal number mutations?

There are two main types of chromosomal number mutations – aneuploidy and polyploidy. 

Aneuploidy: This type of number chromosomal mutation is generally caused due to nondisjunction during meiosis or mitosis, resulting in either the addition of a chromosome (hyperploidy) or loss of a chromosome (hypoploidy). Down Syndrome is a common example of aneuploidy.  

Polyploidy: This type of number chromosomal mutation results in the creation of two sets of genomes within an organism. This is a relatively rare chromosomal mutation and is only observed in a few plants. Gigantism and reduced fertility are two common examples of polyploidy.