Section 1 Section 2 Section 3 Misc. Search

Chromosome Mutation

Chromosomes come in pairs with half of each inherited from each parent. Each cell of an organism have the same number of chromosomes except the gametes, which only have half as many chromosomes as the somatic (body) cells. However, size and number of chromosomes vary among species. Chromosome mutations are different from gene mutations in that a spontaneous modification results in more pronounced effects.

Chromosomal mutations take place when the number of chromosomes changes or when structural changes occur in the chromosomes. This process occurs generally during the formation of a zygote where changes in the number of chromosomes may result in fission (two into one or one into two) or fusion (two into one).

Structural changes in chromosomes may occur in several ways including inversion, in which a chromosomal segment rotates 180-degrees around the same point, duplication, in which the addition of a chromosomal segment occurs and deletion, in which the loss of a segment results. The shifting of chromosomal segments is known as translocation.

These process do not change the amount of DNA in an organism and their importance to evolution is their contribution to variability via a change in the pattern of gene interaction.

A common example of chromosomal mutation in humans is the Down’s syndrome where a person has either one less or one more chromosome.