chronic fatigue syndrome A debilitating and complex disorder characterized by profound fatigue that lasts 6 months or longer, is not improved by bed rest, and may be worsened by physical or mental activity. Abbreviated CFS. Persons with CFS most often function at a substantially lower level of activity than they were capable of before the…
chronic disease A disease that persists for a long time, typically 3 months or more. Examples of chronic diseases include arthritis, diabetes, and emphysema. In comparison, an acute illness is of short duration. See also acute.
chronic bronchitis See bronchitis, chronic.
chronic arthritis, systemic-onset juvenile See Still’s disease.
chronic In medicine, lasting a long time. A chronic condition is one that lasts 3 months or more. Chronic diseases are in contrast to those that are acute (abrupt, sharp, and brief) or subacute (within the interval between acute and chronic).
chromosomes in multiple miscarriages Chromosome abnormalities (such as deletions, additions, or translocations) that are responsible for causing miscarriages. A couple that has had more than one miscarriage has about a 5 percent chance that one member of the couple is carrying an irregular chromosome that is responsible for the miscarriages.
chromosome map The chart of the linear array of genes on a chromosome. The Human Genome Project contributes to the mapping of the human chromosomes. See also Human Genome Project.
chromosome inversion, pericentric A basic type of chromosome rearrangement in which a segment that includes the centromere (and is therefore pericentric) is snipped out of a chromosome, inverted, and inserted back into the chromosome. The feature that makes it pericentric is that the breaks are on both sides of the centromere.
chromosome inversion, paracentric A type of chromosome rearrangement in which a chromosomal segment that does not include the centromere (and is therefore paracentric) is snipped out of a chromosome, inverted, and inserted back into the chromosome. The feature that makes it paracentric is that both breaks are on the same side of the centromere, so…
chromosome inversion A condition in which a chromosome segment is clipped out, turned upside down, and reinserted back into the chromosome. A chromosome inversion can be inherited from one or both parents, or it may be a mutation that appears in a child whose family has no history of chromosome inversion. An inversion can be…
chromosome disorder An abnormal condition due to something unusual in an individual’s chromosomes. For example, Down syndrome is a chromosome disorder caused by the presence of an extra copy of chromosome 21, and Turner syndrome is most often due to the presence of only a single sex chromosome: one X chromosome.
chromosome complement The whole set of chromosomes for a species. In humans, the normal chromosome complement consists of 46 chromosomes, including the 2 sex chromosomes. Also known as the karyotype.