==염색체의 구조 이상==
When the chromosome's structure is altered, this can take several forms:
A portion of the chromosome is missing or deleted. Known disorders in humans include [[Wolf-Hirschhorn syndrome]], which is caused by partial deletion of the short arm of chromosome 4; and [[Jacobsen syndrome]], also called the terminal 11q deletion disorder.
A portion of the chromosome is duplicated, resulting in extra genetic material. Known human disorders include [[Charcot-Marie-Tooth#Types of the disease|Charcot-Marie-Tooth disease type 1A]] which may be caused by duplication of the gene encoding [[peripheral myelin protein 22]] (PMP22) on chromosome 17.
A portion of one chromosome is transferred to another chromosome. There are two main types of translocations:
**[[Chromosomal translocation#Reciprocal (non-Robertsonian) translocations|Reciprocal translocation]]: Segments from two different chromosomes have been exchanged.
**[[Robertsonian translocation]]: An entire chromosome has attached to another at the centromere - in humans these only occur with chromosomes 13, 14, 15, 21 and 22.
A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted.
*[[Insertion (genetics)|Insertions]]: A portion of one chromosome has been deleted from its normal place and inserted into another chromosome.
*[[Ring chromosome|Rings]]: A portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.
*[[Isochromosome]]: Formed by the mirror image copy of a chromosome segment including the centromere.
[[Chromosome instability syndrome]]s are a group of disorders characterized by chromosomal instability and breakage. They often lead to an increased tendency to develop certain types of malignancies.