Study, linkage
A study aimed at establishing linkage between genes. 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.
Today linkage studies serve as ways of gene-hunting and genetic testing.
Read Also:
- Study, longitudinal
A study done over the passage of time. For example, a longitudinal study of children with Down syndrome (trisomy 21) might involve the study of 100 children with this condition from birth to 10 years of age. Also called a diachronic study. The opposite of a cross-sectional (synchronic) study.
- Study, preclinical
A study to test a drug, procedure or medical treatment in animals. The aim is to collect data in support of safety. Preclinical studies are required before clinical trials can be started.
- Study, stomach emptying
Also called a gastric emptying study, this test evaluates the emptying of food from the stomach. For a gastric emptying study, a patient eats a meal in which the solid food, liquid food or both are mixed with a small amount of radioactive material. A scanner (acting like a Geiger counter) is placed over the […]
- Stuffy nose
The presence of increased secretions and mucus in the nasal passages, most commonly arising as a result of a common cold, allergic reaction, or inflammation or infection of the paranasal sinuses (sinus infection).
- Sturge-Weber syndrome
A congenital, but not inherited, disorder that affects the skin, the neurological system, and sometimes the eyes. The main sign of Sturge-Weber syndrome is a port wine stain birthmark. Neurological symptoms may include seizures and developmental delay. Also known as encephalotrigeminal angiomatosis. See also port wine stain.