When there is a mutation in the genes that make up a person's DNA, a genetic disorder can - but does not always - emerge. Because the mutation impacts the gene's ability to make a protein, this vital element of life can be altered in some way or be missing altogether; in these cases, a genetic disorder often follows. There are three general types of genetic disorders: single-gene disorders occur when a mutation only has an impact on one specific gene; chromosomal disorders are when chromosomes (either individually or in pairs) are altered or missing; and complex disorders, occurring when mutations are present in two or more genes. Each type of genetic disorder manifests in different ways, impacting the individual and their quality of life in just as many variations as the disorders themselves.
The mutations that cause genetic disorders can occur at various points. Some mutations are inherited from parents and their DNA; the corresponding genetic disorder is present from birth. One such genetic disorder is sickle cell disease. Other genetic disorders are caused by mutations that occur at some point in a person's life; this mutation can be due to environmental factors, cancers, or a host of other causes. The former of these is the more common type of genetic disorder, and it usually affects a specific gene; cystic fibrosis and Tay-Sachs disease, for example, are genetic disorders that manifest as a result of mutations in very specific genes. It is only in rare cases that these inherited genetic disorders are passed from parent to child with the parent is not a carrier of the mutation. The culprit, then, is a mutation in the egg or sperm that occurs before conception. Other genetic disorders are referred to as multifactorial inheritance disorders; these are rooted in genetic mutations impacting a series of mutations in various genes coupled with environmental factors. The research on genetic disorders is complex, but thankfully is always evolving as new evidence is discovered in the areas of identification, treatment, and prevention.