A genetic disorder is a disease caused by abnormalities in one's genome, or genetic material. Genetic disorders are broken down into four different type: single-gene, multifactorial, chromosomal, and mitochondrial.
Single-gene disorders are caused by mutations or changes that occur in the DNA grouping of a gene. These disorders occur when cells are unable to produce necessary proteins needed to change certain chemicals into others or to carry substances from one place to another. The cell's inability to carry out these functions often results in mental retardation. Almost 1 in every 5000 children is born with defective enzymes resulting in this disorder. There are more than 6000 known single-gene disorders.
Sometimes mental retardation is caused by a combination of genetic problems and evnironmental factors. This is called multifactorial disorder. Their inheritance patterns are usually complex because not only does the presence of heredity matters, but also the environmental factors. Weight, height, fingerprint patterns, eye color, skin color, and intelligence are traits inherited in this way. Some of the most common chronic disorders are multifactorial disorders. Examples of multifactorial disorders include cancer, high blood pressure, heart disease, diabetes, Alzheimer's disease, and obesity.
Chromosomes are structures made up of DNA and protein. They are located in the nucleus of each cell. Because chromosomes are carriers of the genome, such abnormalities in chromosome structure such as missing or extra copies or translocations often result in disease. Although they are considered genetic disorders, they are not necessarily inherited, for in most cases each of the parent's gene is normal. It is thought to be that during cell division, an error in separation, recombination or distribution of chromosomes occurs. Chromosomal disorders affect approximately 7 out of every 1000 infants. 50% of all first-trimester miscarriages or spontaneous abortions occur as a result of a chromosome abnormality.