| Bombay trait | A rare recessive trait at a locus that ordinarily manufactures H substance, the precursor from which the A and B phenotypes are elaborated; the mutant causes failure to produce H substance and no matter what the genotype at the ABO locus, the phenotype is O. The Bombay phenomenon is epistatic to the ABO locus. Origin: Bombay, India, where first reported (05 Mar 2000) |
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| galtonian trait | A quantitative genetic trait due to contributions from many more of less equally important loci that resembles a continuous trait. (05 Mar 2000) |
| recessive trait | See: dominance of traits. (05 Mar 2000) |
| marker trait | A trait that may be of little importance in itself but which by association, linkage, or other means facilitates the detection, anticipation, or understanding of a disease or (for genetic diseases) the localization of the causative gene on the karyotype. (05 Mar 2000) |
| categorical 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) |
| penetrant trait | A trait that in the appropriate genotypes is phenotypically manifest; strictly, it is the trait that is penetrant, not the gene. See: penetrance. (05 Mar 2000) |
| mendelian trait | A categorical trait that segregates in accordance with a single-locus genetic system. (05 Mar 2000) |
| 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) |
| 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) |
| quantitative trait | A characteristic showing quantitative inheritance such as skin pigmentation in man. (12 Dec 1998) |
| 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) |