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.
- Linkage map
A map of the genes on a chromosome based on linkage analysis. A linkage map does not show the physical distances between genes but rather their relative positions, as determined by how often two gene loci are inherited together. The closer two genes are (the more tightly they are linked), the more often they will […]
- Lip, cleft
A fissure in the upper lip that is due to failure of the left and right sides of the fetal lip tissue to fuse, an event that should take place by 35 days of fetal age. Cleft lip can be on one side only or on both sides. Because failure of lip fusion can impair […]
- Lipectomy, suction-assisted
Another name for liposuction, the surgical removal of fat deposits from specific parts of the body, the most common being the abdomen (the “tummy”), buttocks (“behind”), hips, thighs and knees, chin, upper arms, back, and calves. The technique breaks up and “sucks” fat out of the body through a canula (a hollow instrument) inserted subdermally […]
Another word for “fat.” (Please see the various meanings of fat.) A lipid is chemically defined as a substance that is insoluble in water and soluble in alcohol, ether, and chloroform. Lipids are an important component of living cells. Together with carbohydrates and proteins, lipids are the main constituents of plant and animal cells. Cholesterol […]
- Lipid profile
A pattern of lipids in the blood. A lipid profile usually includes the levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, and the calculated low-density lipoprotein (LDL) ‘cholesterol.