| selectable marker | <molecular biology> A gene whose expression allows one to identify cells that have been transforrned or transfected with a vector containing the marker gene. (09 Oct 1997) |
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| Selected Area Electron Diffraction | <technique> In this diffraction mode an aperture is used to define the area from which a diffraction pattern is to be recorded from a thin sample. This aperture is typically located in an image plane below the sample. Selected Area Electron Diffraction patterns are simple spot patterns and are of use in phase determination (lattice spacing measurement) and defect analysis (sample orientation). Acronym: SAED (05 Aug 1998) |
| selectin | <protein> Group of cell adhesion molecules that bid to carbohydrates via a lectin like domain. The name is derived from select and lectin. They are integral membrane glycoproteins with an N terminal, C type lectin domain, followed by an EGF like domain, a variable number of repeats of the short consensus sequence of complement regulatory proteins and a single transmembrane domain. Three selectins have been identified and are distinguished by capital letters based on the source of the original identification i.e. E selectin, L selectin and P selectin. (18 Nov 1997) |
| selectins | Family of cell adhesion molecules consisting of a lectin-like domain, an epidermal growth factor-like domain, and a variable number of domains that encode proteins homologous to complement-binding proteins. Selectins mediate the binding of leukocytes to the vascular endothelium. (12 Dec 1998) |
| selection | <biology> Placing organisms under conditions where the growth of those with a particular genotype will be favored. (09 Oct 1997) |
| selection (genetics) | Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population. (12 Dec 1998) |
| selection bias | The introduction of error due to systematic differences in the characteristics between those selected and those not selected for a given study. In sampling bias, error is the result of failure to ensure that all members of the reference population have a known chance of selection in the sample. (12 Dec 1998) |
| selection coefficient | The proportion of progeny or potential progeny not surviving to sexual maturity; usually defined artificially by expressing the fitness of a phenotype as a fraction of the mean or optimal fitness to give the relative fitness, and subtracting this fraction from unity. If the mean size of family in the population is 3.2 and that for a particular genotype is 2.4 then the fitness of the phenotype is 2.4/3.2 =0.75 and the selection coefficient =1-0.75 =.25 = 5 (05 Mar 2000) |
| selection cutting | The periodic removal at short intervals of the oldest and largest trees in the stand, individually or in small groups. (05 Dec 1998) |
| selection pressure | Impact of effective reproduction due to environmental impact on the phenotype. (05 Mar 2000) |
| selective angiography | <procedure, radiology> Angiography in which visualization is improved by concentrating the contrast medium in the region to be studied by injection through a catheter positioned in a regional artery. (05 Mar 2000) |
| selective grinding | <dentistry> The modification of the occlusal forms of teeth by grinding according to a plan or by grinding at selected places marked by articulating ribbon or paper. (05 Mar 2000) |
| selective hypoaldosteronism | <endocrinology> Isolated hypoaldosteronism, aldosterone deficiency without a concomitant deficiency of glucocorticoid hormones. (05 Mar 2000) |
| selective immunoglobulin A deficiency | <immunology> An inherited disorder in which there is a markedly reduced or absent IgA, resulting in immature IgA-bearing B-cells. (05 Mar 2000) |
| selective inhibition | <chemistry> Inhibitor that occupies the active site of an enzyme or the binding site of a receptor and prevents the normal substrate or ligand from binding. at sufficiently high concentration of the normal ligand inhibition is lost: the Km is altered by the competitive inhibitor, but the Vmax remains the same. (05 Jan 1998) |