Dictionary > Allelic exclusion

Allelic exclusion

Allelic exclusion
(Science: cell biology, genetics) The process whereby one or more loci on one of the chromosome sets in a diploid cell is inactivated (or destroyed) so that the locus or loci is (are) not expressed in that cell or a clone founded by it.
For example in mammals one of the x chromosome pairs of females is inactivated early in development (see Lyon hypothesis) so that individual cells express only one allelic form of the product of that locus. Since the choice of chromosome to be inactivated is random, different cells express one or other of the x chromosome products resulting in mosaicism.
The process is also known to occur in immunoglobulin genes so that a clone expresses only one of the two possible allelic forms of immunoglobulin.

You will also like...

Chromosome Mutations
Chromosome Mutations

Mutations can also influence the phenotype of an organism. This tutorial looks at the effects of chromosomal mutations, ..

Schematic diagram of DNA replication
DNA Structure & DNA Replication

DNA is a double helix structure comprised of nucleotides. A nucleotide, in turn, is made up of phosphate molecule, deoxy..

Growth Patterns
Growth Patterns

This tutorial describes the sigmoid curve, annual plant growth, tree growth, human growth, and insect growth as the grow..


Stems primarily provide plants structural support. This tutorial includes lectures on the external form of a woody twig ..

Water in Plants

The movement of molecules (specifically, water and solutes) is vital to the understanding of plant processes. This tuto..

Peppered moth ("Biston betularia") melanic and light form
Examples of Natural Selection

Darwin's Finches are an example of natural selection in action. They are an excellent example of the way species' gene p..