| amplification | <molecular biology> An increase in the number of copies of a specific DNA fragment, can be in vivo or in vitro. See: cloning, polymerase chain reaction. (09 Oct 1997) |
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| random amplification of polymorphic DNA | <molecular biology> A term originally invented by polymer chemists to describe a disordered tangle of a linear polymer chain with curved sections. In DNA parlance the random coil refers to the structure that results from melting or other forms of separation of the double helix, i.e. Helix coil transition. (18 Nov 1997) |
| gene amplification | <molecular biology> Selective replication of DNA sequence within a cell, producing multiple extra copies of that sequence. The best known example occurs during the maturation of the oocyte of Xenopus, where the set (normally 500 copies) of ribosomal RNA genes is replicated some 4,000 times to give about 2 million copies. (18 Nov 1997) |
| genetic amplification | A process for producing an increase in pertinent genetic material, particularly for increasing the proportion of plasmid DNA to that of bacterial DNA. Includes the production of extrachromosomal copies of the genes for RNA. (05 Mar 2000) |
| DNA amplification | <molecular biology> The use of enzymes in making millions or billions of copies of a single DNA sequence (see PCR). (14 Nov 1997) |
| ligase amplification reaction | <molecular biology> Method for detecting small quantities of a target DNA, with utility similar to PCR. It relies on DNA ligase to join adjacent synthetic oligonucleotides after they have bound the target DNA. Their small size means that they are destabilised by single base mismatches and so form a sensitive test for the presence of mutations in the target sequence. (18 Nov 1997) |
| programming, linear | A technique of operations research for solving certain kinds of problems involving many variables where a best value or set of best values is to be found. It is most likely to be feasible when the quantity to be optimised, sometimes called the objective function, can be stated as a mathematical expression in terms of the various activities within the system, and when this expression is simply proportional to the measure of the activities, i.e., is linear, and when all the restrictions are also linear. It is different from computer programming, although problems using linear programming techniques may be programmed on a computer. (12 Dec 1998) |
| non-linear | Not linear. (05 Dec 1998) |
| superficial linear keratitis | Spontaneous, painful keratitis with epithelial erosion and folds in Bowman's membrane. (05 Mar 2000) |
| linear | Pertaining to or resembling a line. Origin: L. Linearis (18 Nov 1997) |
| linear absorption coefficient | That fraction of ionizing radiation absorbed in a unit thickness of a substance or tissue. See: absorption coefficient. (05 Mar 2000) |
| linear acceleration | The rate of change of velocity without a change in direction; e.g., when the speed of an aircraft increases while flying a straight pathway. (05 Mar 2000) |
| linear accelerator | <apparatus> A sophisticated external beam radiotherapy machine which has the capabilities of focussing irradiation (although not very finely). Acronym: LinAC (16 Dec 1997) |
| linear amputation | Amputation performed by a circular incision through the skin, the muscles being similarly divided higher up, and the bone higher still. Synonym: guillotine amputation, linear amputation. (05 Mar 2000) |
| linear atrophy | Bands of thin wrinkled skin, initially red but becoming purple and white, which occur commonly on the abdomen, buttocks, and thighs at puberty and/or during and following pregnancy, and result from atrophy of the dermis and overextension of the skin; also associated with ascites and Cushing's syndrome. Synonym: atrophoderma striatum, lineae albicantes, lineae atrophicae, linear atrophy, stretch marks, stria, striae atrophicae, striate atrophy of skin, traction atrophy, vergeture. (05 Mar 2000) |