Analysis, linkage

Study aimed at establishing linkage between genes. Today linkage analysis serves as a way of gene-hunting and genetic testing. Linkage is the tendency for genes and other genetic markers to be inherited together because of their location near one another on the same chromosome. A gene is a functional physical unit of heredity that can be passed from parent to child. All genes in humans are pieces of DNA. Most genes contain information for making a specific protein. The term "genetic marker" is broader than a gene. A genetic marker is simply a segment of DNA with an identifiable physical location on a chromosome whose inheritance can be followed. A genetic marker can have a function and thus be a gene. Or a marker can be a section of DNA with no known function. Because DNA segments that lie near each other on a chromosome tend to be inherited together, markers are often used as tools for tracking the inheritance pattern of a gene that has not yet been identified but whose approximate location is known. The statistical estimate of whether two loci are likely to lie near each other on a chromosome and are therefore likely to be inherited together is called a LOD score. A LOD score of 3 or more is generally taken to indicate that the two loci are linked and are close to one another.