What is a Chromosome Abnormality?
A chromosome abnormality is a change in the number or the arrangement of the chromosomes. There are many different types of possible changes. In some individuals, a piece of a chromosome is missing. This is called a deletion. In other individuals, a piece of a chromosome is duplicated. This is called a duplication. Sometimes, a piece of one chromosome is broken off and attached to another chromosome. This is called a translocation. A person may have an entire extra copy of a chromosome or a missing chromosome. These are called trisomy and monosomy, respectively. There are other types of chromosome abnormalities as well, such as ring chromosomes, insertions, inversions, and isochromosomes (which occur when one half of the chromosome is missing and the other half is duplicated). In most cases, chromosome abnormalities are diagnosed by a karyotype. A geneticist with specialized training looks for any changes in the number or arrangement of the chromosomes. What Is and Isn’t a Chromosome A
