In recent years researchers have identified a number of chromosomes that appear to have an involvement in the development of Parkinson’s disease. A chromosome is a cellular structure that contains hundreds or thousands of genes, which are the base units of inherited information that determine many of the characteristics of an individual’s existence. A normal cell contains 23 pairs of chromosomes; in health, the pairs have identical structure, except for the unmatched X-Y sex chromosomes in men (women have matched X-X sex chromosomes). Each cell repeats this pairing and structure (except ova, or eggs, and sperm, which each contain half the chromosomes and blend to create a full chromosomal complement at conception).
Genes line each chromosome in a particular and identical order for every appearance of that chromosome in every cell. All of the genes on chromosome 4, for example, are in exactly the same location on every chromosome 4 in every cell. It is this consistent presence that allows the characteristics of their genetic coding to manifest, somewhat in the way that aligning tumblers in a lock allows the lock to open. If just one tumbler is out of alignment, the lock does not open. Such is the case with genes and chromosomes, although of course in a much more intricate and complex manner; all must be precisely aligned to display their characteristics.
There can be mutations (changes or “errors” in the gene’s content) of a particular gene that appear in that gene in every cell or minor aberrations in a single presence of the gene. Generally single aberrations do not interfere with health although mutations create differences that can be either benign or harmful.
Locating the chromosome in which the genes responsible for certain traits reside is the first step in identifying and possibly correcting gene mutations that cause diseases. The extent to which gene mutations cause Parkinson’s disease remains unknown. Most researchers believe it is a combination of genetic and environmental factors that converge to permit Parkinson’s to develop. Recent research suggests that genetic factors might be more prevalent and significant than long assumed, however. Scientists can now link mutations in defined areas on chromosomes 1, 2, 4, 5, 6, 8, 9, and 17 to Parkinson’s disease, although the role that these mutations play and the specific genes that are involved remain unclear.
Researchers discovered the parkin gene, located on chromosome 6, in the 1990s and subsequently have discovered a number of other genes that seem specific to Parkinson’s disease, particularly early-onset Parkinson’s, in some way. Some of these genes relate only to Parkinson’s, and others have broader effects on health and disease throughout the body. As technology is rapidly evolving to allow more precise examination of chromosomal and genetic structures, there is a continuous stream of new discoveries about the extent to which genetic factors influence Parkinson’s disease regardless of the age of onset. These are spawning a number of experimental gene therapies that show great promise for changing the course of Parkinson’s disease and strengthen HOPE FOR A CURE FOR PARKINSON’S.