What are some types of chromosomal disorders?

Chromosomal disorders are a result of an alteration in genetic material. These alterations can be grouped into three categories: error in number, deletions and point mutations.

Error in the number of chromosomes (too many or too few) includes the following disorders:

• Down’s syndrome or trisomy 21: The individual has an extra chromosome 21.
• Trisomy 18 or Edwards’s syndrome: The individual has an extra chromosome 18.
• Trisomy 13 or Patau syndrome: The individual has an extra chromosome 13
• Turner’s syndrome: Girls with Turner syndrome have one X chromosome and are missing all or part of the other X chromosome
• Klinefelter syndrome: Boys with Klinefelter syndrome have two, or occasionally more, X chromosomes along with their Y chromosome.

Deletion of a genetic material on a specific chromosome such as:

• Cri-du-chat (cat cry) syndrome: the individual is missing the short arm on chromosome 5
• Prader-Willi syndrome: The individual has a deletion on chromosome 15

Point mutation or any insertion/deletion entirely inside one gene examples include:

• Color blindness: Carried on the X chromosome and males with the gene have the disorder.
• Cystic fibrosis: Carried on chromosome 7 as a recessive trait.
• Tay–Sachs disease: Carried on chromosome 15.

There are many types of chromosomal disorders. The most common is Down syndrome, which is most often caused by an extra copy of chromosome 21. Fragile X is a disorder that has DNA abnormalities on the X chromosome. In boys, the abnormality is most often inherited from their mother. Kleinefelter's syndrome occurs when boys are born with an extra X chromosome and may cause complications at puberty. Children with Turner's syndrome are born missing part of or a whole X chromosome. These are only a few chromosomal disorders; there are rarer disorders as well.