What happens if a human has an extra chromosome?

For example, an extra copy of chromosome 21 causes Down syndrome (trisomy 21). Chromosomal abnormalities can also cause miscarriage, disease, or problems in growth or development. The most common type of chromosomal abnormality is known as aneuploidy, an abnormal chromosome number due to an extra or missing chromosome.

What does trisomy mean?

The term “trisomy” is used to describe the presence of an extra chromosome — or three instead of the usual pair. For example, trisomy 21 or Down syndrome occurs when a baby is born with three #21 chromosomes. In trisomy 18, there are three copies of chromosome #18 in every cell of the body, rather than the usual pair.

What are the most common chromosomal disorders?

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 .

What diseases are caused by chromosomal mutations?

But the mutations we hear about most often are the ones that cause disease. Some well-known inherited genetic disorders include cystic fibrosis, sickle cell anemia, Tay-Sachs disease, phenylketonuria and color-blindness, among many others. All of these disorders are caused by the mutation of a single gene.

How are chromosomal diseases diagnosed?

Chromosomal disorders are generally identified through family history screenings and prenatal screenings. When a chromosomal abnormality appears likely, a doctor will perform a diagnostic chromosomal analysis on blood, cells from the amniotic fluid, or chorionic villus samplings.

What genetic disorder is missing a chromosome?

Deletions: 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.