What is Trisomy

Trisomy is known as a genetic disorder/syndrome, chromosome disorder or chromosomal anomaly. Chromosomes are found in the nucleus of all body cells and carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males, and two X chromosomes for females. People with a Trisomy have an extra chromosome added to one of the normal pairs. Each chromosome has a short arm that is designated "p" and a long arm identified by the letter "q". The triplication of the chromosome may be partial; i.e., with only a portion of the chromosome duplicated. Defects are classified by the name of the abnormal chromosome pair and which portion of the chromosome is affected. For example, Noah had partial Trisomy of 2p+ which means that he had a partial extra short arm added to the 2nd pair of chromosomes. In general, the most common symptom of the trisomies is mental retardation. Basically, the presence of an extra chromosome, such as is found in Trisomy, results in a characteristic pattern of birth defects and medical problems that is recognized as a syndrome. The best known and best studied of these Trisomy conditions is Trisomy 21, more commonly known as Down Syndrome.