Fragile sites A non-staining gap of variable width that usually involves both chromatids and is always at exactly the same point on a specific chromosome derived from an individual or kindred. Functional gene tests Biochemical assays for a specific protein, indicating a specific gene is not merely present but active. Each of the body's 50,000 to 100,000 genes contains the code for a specific product, typically, a protein such as an enzyme. The total loss or absence of a gene. Gene families Groups of closely related genes that make similar products.
Gene library See genomic library.
Gene mapping Determining the relative positions of genes on a chromosome and the distance between them. The biochemical material, either RNA or protein, resulting from expression of a gene. Gene testing Examining a sample of blood or other body fluid or tissue for biochemical, chromosomal, or genetic markers that indicate the presence or absence of genetic disease. In early studies of gene therapy for cancer, researchers are trying to improve the body's natural ability to fight the disease or to make the tumor more sensitive to other kinds of therapy. Addition of a functional gene or group of genes to a cell by gene insertion to correct an hereditary disease.