| chromosomal trait | A trait dependent on a recurrent chromosomal aberration. (05 Mar 2000) |
|---|---|
| codominant trait | See: codominant. (05 Mar 2000) |
| sickle cell trait | <haematology> This condition occurs in people who have one of two possible genes (i.e., they are heterozygous forthe allele) that code for the defective haemoglobin responsible for sickle cell anaemia. The coditionis diagnosed by exposing an individual's red blood cells to a low oxygen environment, if the trait is present, the cells will turn to a sickle shape. People with this trait may suffer milder symptoms of sickle cell anaemia, or may have no symptoms. Some scientists believe the trait actually provides an evolutionary advantage in tropical environments because the slightly altered shape of the blood cells causes a person to be more resistant to malaria. (09 Oct 1997) |
| nonpenetrant trait | A genetic trait that is not phenotypically manifest because of non-genetic factors it therefore does not include recessivity, epistasis, hypostasis, or parastasis but does include environmental factors and pure random effects such as lyonization. (05 Mar 2000) |
| dominant lethal trait | Trait, expressed in the phenotype if present in the genotype, that precludes having descendants. All such cases are necessarily sporadic and must represent new mutations as the usual methods of classical genetics provide no means of demonstrating any genetic component whatsoever, except for tenuous arguments such as advanced paternal age. Molecular biology may help although the methods may be tedious; if there is an epistatic gene that may mask the trait, the logic is more tractable, though complex. (05 Mar 2000) |
| dominant trait | An outstanding mental or physical characteristic. See: dominance of traits. (05 Mar 2000) |
| qualitative trait | <genetics> A feature that can conveniently and effectively be analyzed by sorting into classes either because there is no satisfactory way of measuring it (as with blood groups) or because it falls into natural classes so that the variation among classes far exceeds that within classes (e.g., the phenotypic effects of many enzyme polymorphisms); existence of categories suggests but does not prove the operation of a major, simple, underlying cause. Synonym: qualitative trait. (05 Mar 2000) |
| intermediate trait | A measurable trait in which there is some evidence of the operation of a simple major cause, but in which the variation within the putative categories is such as to cause overlap and hence ambiguity in classification of any particular reading. (05 Mar 2000) |
| threshold trait | A trait that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. Synonym: liminal trait. (05 Mar 2000) |
| trait | A qualitative characteristic; a discrete attribute as contrasted with metrical character. A trait is amenable to segregation rather than quantitative analysis; it is an attribute of phenotype, not of genotype. Origin: Fr. From L. Tractus, a drawing out, extension (05 Mar 2000) |
| liminal trait | A trait that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. Synonym: liminal trait. (05 Mar 2000) |