chromosomal mutation

chromosomal mutation

changes to the chromosome complement or structure of cells or organisms. There are two major types:

1. numerical, affecting whole chromosomes (see POLYPLOID and ANEUPLOIDY), and
2. structural, affecting genetic arrangement within chromosomes. These are usually of a fairly major type (compare POINT MUTATION) and often cause severely adverse effects. Such structural mutations are classified into various types:

1. inversion, the rearrangement of a chromosomal segment so that it has the reverse sequence, e.g. ABCDE ----> ADCBE;
2. deletions, the removal of a segment;
3. duplication, the repeating of a segment either next door to the original or elsewhere along the chromosome;
4. translocation, the exchange of segments between nonhomologous chromosomes.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005