| effect, founder | A population group with an unusual frequency of a gene due to there having been only a small number of original members ( founders ) one or more of whom had that gene. For example, the gene for Huntington disease was introduced into the Lake Maracaibo region of Venezuela early in the 19th century, so there are now over a hundred persons with Huntington disease and at least 900 persons at risk for that deadly disease in that region, the largest known aggregation known in the world with the Huntington gene. (12 Dec 1998) |
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| founder effect | The establishment of a new population by a few original founders (in an extreme case, by a single fertilized female) which carry only a small fraction of the total genetic variation of the parental population [Ernst Mayr, 1963]. The result is that a given allele, gene, chromosome, or part of a chromosome found in members of the population can be traced back to one ancestral individual. (09 Oct 1997) |
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| brass founder's ague | An occupational disease, characterised by malaria-like symptoms, due to inhalation of particles and fumes of metallic oxides. Fumes are formed by evaporation at very high temperature and condensation in air into fine particles. Synonym: brass founder's ague, foundryman's fever, metal fume fever, zinc fume fever. (05 Mar 2000) |
| brass founder's fever | An occupational disease, characterised by malaria-like symptoms, due to inhalation of particles and fumes of metallic oxides. Fumes are formed by evaporation at very high temperature and condensation in air into fine particles. Synonym: brass founder's ague, foundryman's fever, metal fume fever, zinc fume fever. (05 Mar 2000) |
| founder | <veterinary> A lameness in the foot of a horse, occasioned by inflammation; closh. An inflammatory fever of the body, or acute rheumatism; as, chest founder. Source: Websters Dictionary (01 Mar 1998) |
| founder cell | Cell that gives rise to tissue by clonal expansion. For most mammalian tissues there are considerably more than two founder cells, as can be determined by forming chimeras from genetically distinguishable embryos, but single founder cells have been found for the intestine and germ line in Caenorhabditis elegans. (18 Nov 1997) |
| founder principle | The conditional probabilities of the frequencies of a set of genes at any future date depend on the initial composition of the founders of the population and have in general no tendency to revert to the composition of the population from which the founders were themselves derived. (05 Mar 2000) |
| abscopal effect | A reaction produced following irradiation but occurring outside the zone of actual radiation absorption. (05 Mar 2000) |
| additive effect | <biochemistry, chemistry> An additive effect is the overall biological effect two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. Compare: antagonism. (15 Jan 1998) |
| adverse effect | This is an abnormal or harmful effect to an organism caused by exposure to a chemical. It is indicated by some result such as death, a change in food or water consumption, altered body and organ weights, altered enzyme levels, or visible illness. An effect may be classed as adverse if it causes functional or anatomical damage, causes irreversible change in the homeostasis of the organism, or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when the organism is no longer being exposed to the chemical. (09 Oct 1997) |
| Anrep effect | A small transient positive inotropic effect of abrupt increases of systolic aortic and left ventricular pressures related to recovery from transient subendocardial ischemia (e.g., cold pressor test). (05 Mar 2000) |
| antagonistic effect | This is the consequence of one chemical (or group of chemicals) counteracting the effects of another chemical, the opposing chemicals cancel out each other's effects. (09 Oct 1997) |
| Arias-Stella effect | Focal, unusual, decidual changes in endometrial epithelium, consisting of intraluminal budding, and nuclear enlargement and hyperchromatism with cytoplasmic swelling and vacuolation; may be associated with ectopic or uterine pregnancy. Synonym: Arias-Stella effect, Arias-Stella reaction. (05 Mar 2000) |
| Auger effect | <physics> Transition of an electron in an atom from a discrete electronic level to an ionised continuous level with the same energy. Synonym: autoionisation. (13 Jan 1998) |
| autokinetic effect | In psychology, the apparent drifting about of a small, fixed, spot of light which is being observed in a dark room. (05 Mar 2000) |
| Bernoulli effect | <physics> The decrease in fluid pressure that occurs in converting potential to kinetic energy when motion of the fluid is accelerated, in accordance with Bernoulli's law. Applied in water aspirators, atomisers, and humidifiers in which a gas is accelerated across the end of a narrow, fluid-filled orifice. (05 Mar 2000) |