| enhancer trap | <molecular biology, technique> Technique for mapping gene expression patterns, classically in Drosophila. A transposon element carrying a reporter gene (usually _ galactosidase), linked to a very weak promoter, is induced to jump within the genome. If the P element re inserts within the sphere of influence of promoters and enhancers of some (random) gene, then reporter gene is also expressed in a similar tissue specific manner. Usually, many lines of flies carrying such random insertions are studied, if a line shows interesting patterns of expression, it can be possible to clone the gene of interest. (18 Nov 1997) |
|---|
| drain-trap stomach | water-trap stomach |
|---|---|
| trap | <geology> An old term rather loosely used to designate various dark-coloured, heavy igneous rocks, including especially the feldspathic-augitic rocks, basalt, dolerite, amygdaloid, etc, but including also some kinds of diorite. Called also trap rock. Trap tufa, Trap tuff, a kind of fragmental rock made up of fragments and earthy materials from trap rocks. Origin: Sw. Trapp; akin to trappa stairs, Dan. Trappe, G. Treppe, D. Trap; so called because the rocks of this class often occur in large, tabular masses, rising above one another, like steps. See Tramp. 1. A machine or contrivance that shuts suddenly, as with a spring, used for taking game or other animals; as, a trap for foxes. "She would weep if that she saw a mouse Caught in a trap." (Chaucer) 2. A snare; an ambush; a stratagem; any device by which one may be caught unawares. "Let their table be made a snare and a trap." (Rom. Xi. 9) "God and your majesty Protect mine innocence, or I fall into The trap is laid for me!" (Shak) 3. A wooden instrument shaped somewhat like a shoe, used in the game of trapball. It consists of a pivoted arm on one end of which is placed the ball to be thrown into the air by striking the other end. Also, a machine for throwing into the air glass balls, clay pigeons, etc, to be shot at. 4. The game of trapball. 5. A bend, sag, or partitioned chamber, in a drain, soil pipe, sewer, etc, arranged so that the liquid contents form a seal which prevents passage of air or gas, but permits the flow of liquids. 6. A place in a water pipe, pump, etc, where air accumulates for want of an outlet. 7. A wagon, or other vehicle. 8. A kind of movable stepladder. Trap stairs, a staircase leading to a trapdoor. <botany> Trap tree the jack; so called because it furnishes a kind of birdlime. See 1st Jack. Origin: OE. Trappe, AS. Treppe; akin to OD.trappe, OHG. Trapo; probably fr. The root of E. Tramp, as that which is trod upon: cf. F. Trappe, which is trod upon: cf. F. Trappe, which perhaps influenced the English word. Source: Websters Dictionary (01 Mar 1998) |
| HIV enhancer | Cis-acting regulatory sequences in the HIV long terminal repeat (ltr) which play a major role in induction or augmentation of HIV gene expression in response to environmental stimuli such as mitogens, phorbol esters, or other viruses. The HIV enhancer is the binding site for many cellular transcription factors including the nuclear factor nf-kappa b. (12 Dec 1998) |
| enhancer element | <molecular biology> A DNA sequence, present in the genomes of higher eukaryotes and of various animal viruses, which can increase the transcription of genes into messenger RNA. These control element frequently found 5' to the start site of a gene, when bound by a specific transcription factor, enhance the levels of expression of the gene, but are not sufficient alone to cause expression. Distinguished from a promoter, that is alone sufficient to cause expression of the gene when bound, in practice, the two terms merge. Enhancers usually can function in either orientation and at various distances from a promoter. Compare: promoter. (03 Jul 1999) |
| enhancer sequence | <molecular biology> A nucleotide sequence, located as many as several thousand base pairs away in either direction from the target gene, which enhances transcription of that gene. (14 Nov 1997) |