Inherited Disorders

Some inherited diseases are attributed to damaged or improperly distributed chromosomes and are termed chromosomal diseases. Chromosomes are long strands of DNA complexed with proteins and RNA that condense and allow for equal distribution of the genes when cells divide. Each chromosome contains hundreds or thousands of genes, and every cell needs to have two copies of each chromosome in order to maintain genetic balance. At the time of conception, an extra copy or missing copy of a chromosome or even a part of a chromosome disrupts normal development. Most chromosomal abnormalities result from simple accidents of chromosome segregation and, as such, they tend not to recur in families. One example of genetic disorder that results from chromosomal imbalance is Down syndrome. This condition is caused by the presence of an extra copy of chromosome 21.