Common Chromosome Abnormalities

Chromosomes are the structures that hold genes. There are 46 chromosomes in total, which are grouped into 23 pairs. The first 22 pairs are numbered largest to smallest (1 - 22) and are called autosomes. The last pair determines gender, and is either XX (female) or XY (male).

Chromosome abnormalities are genetic conditions that are caused by abnormalities in chromosome number or structure. Examples of common chromosome abnormalities include:

- Down syndrome - occurs when there is an extra copy of chromosome 21

- Turner Syndrome - occurs when a female has a missing X chromosome (45, X)

- Klinefelter syndrome - occurs when a male has an extra X chromosome (47, XXY)

- Triploidy - occurs when there is an entire extra set of chromosomes for a total of 69 chromosomes

- Markers - occurs when there is an extra piece of chromosome material which can be derived from any chromosome number

- Ring chromosomes - occurs when the arms of a chromosome fuse together to form a ring

- Chromosome Translocation - occurs when an entire chromosome or a piece of a chromosome becomes attached to or interchanged with another whole chromosome or piece of a chromosome

- Chromosome Inversion - occurs when a chromosome breaks in two places and the resulting piece of genetic material is reversed and re-inserted into the chromosome

- Chromosome Deletion - occurs when a chromosome breaks and some genetic material is lost

- Chromosome Duplication - occurs when part of a chromosome is duplicated resulting in extra genetic material from the duplicated piece

For more information about chromosome abnormalities and genetic testing for chromosome abnormalities, visit: http://AccessDNA.com/condition/Chromosome_Abnormalities_/159