Dictionary > Allelism

Allelism

Definition
noun, plural: allelisms
The condition of alleles, such as the state of having several forms of a particular gene, often as a result of mutation
Supplement
Alleles are the pairs of genes occupying a specific spot called locus on a chromosome. Allelism refers to any of the several forms of a gene. These genetic variations arise usually through mutation and therefore are responsible for hereditary variations. Typically, there are only two alleles for a gene in a diploid organism. When there is a gene existing in more than two allelic forms this condition is referred to as multiple allelism. In particular, multiple allelism is the condition wherein three or more alleles of a gene are present. Multiple allelism is best illustrated by the ABO blood group system in humans. In the inheritance of ABO blood group in humans, gene I (I, i.e. isohaemagglutinin) exists in three allelic forms: IA, IB, and IO. IA and IB are codominant. They are responsible for type A and type B antigens, respectively, on the cell surface of erythrocytes. IO is a recessive allele and does not produce antigen. It should be noted though that even if there are more than two alleles present in the population, the individual comprising the population would possess only two such alleles. Thus, in the case of ABO blood group system, the inheritance of IA and IB alleles results in having a blood type AB.
Synonym(s):

  • allelomorphism

See also:

  • allele
  • mutation
  • heredity


    You will also like...

    Plant biology
    Plant Biology

    Plantlife can be studied at a variety of levels, from the molecular, genetic and biochemical level through organelles, c..

    Types and Causes of Brain Damage
    Types and Causes of Brain Damage

    This tutorial describes the different types and causes of brain damage. Find out how genetics, physical injury, lack of ..

    Sugar Homeostasis
    Sugar Homeostasis

    The blood sugar level is regulated by two hormones. The mechanism behind this type of negative feedback control is descr..

    Human perception in action
    Human Perception – Neurology

    This tutorial investigates perception as two people can interpret the same thing differently. Know more about human perc..

    Salmon jumping upstream in the river
    Lotic Communities & Animals

    A running water environment offers numerous microhabitats for many types of animals. Similar to plants, animals in lotic..

    Consciousness and behavior
    Consciousness and Behavior

    Human consciousness and behavior are an interesting topic since they are determined and controlled by the brain. Conscio..