| VNTR | variable number of tandem repeats; variable copy number tandem repeats |
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| DCT | direct Coombs' test; discrete cosine transform; distal convoluted tubule; diurnal cortisol test; dyn... |
| DSAS | discrete subaortic stenosis |
| DSS | dengue shock syndrome; dioctyl sodium sulfosuccinate; Disability Status Scale; discrete subaortic st... |
| DWT | dichotic word test; discrete wave transform |
| random allocation | A process involving chance used in therapeutic trials or other research endeavor for allocating experimental subjects, human or animal, between treatment and control groups, or among treatment groups. It may also apply to experiments on inanimate objects. (12 Dec 1998) |
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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) |
| random amplified polymorphic DNA technique | Technique that utilises low-stringency polymerase chain reaction (pcr) amplification with single primers of arbitrary sequence to generate strain-specific arrays of anonymous DNA fragments. Rapd technique may be used to determine taxonomic identity, assess kinship relationships, analyze mixed genome samples, and create specific probes. (12 Dec 1998) |
| random coil | A structure of a macromolecule (typically, a biopolymer) which changes with time. (05 Mar 2000) |
| random mating | Totally haphazard mating with no regard to the genetic makeup (genotype) of the mate so that any sperm has an equal chance of fertilizing any egg. This rarely, if ever, occurs but the concept is impoortant in population genetics. Also called panmixus. (12 Dec 1998) |
| random mating equilibrium | <genetics> In a population containing the genotypes of AA, aa, and Aa, the frequency of AA will be p2, the frequency of aa will be q2, and the frequency of Aa will be 2 pq at equilibrium, where p is the frequency of A and q is the frequency of a. By the Hardy-Weinberg law, a ramdonly-mating population will eventually reach these frequencies and be at this equilibrium as long as there are no selection pressures on the population. (09 Oct 1997) |
| random mechanism | A scheme for substrate binding and product release for a multisubstrate enzyme; for a two-substrate two-product enzyme with this mechanism, either substrate can bind first and, after the reaction has taken place, either product can be the first to dissociate from the enzyme. Brain hexokinase has a random mechanism. More complex random mechanisms exist for enzymes having more than two substrates. (05 Mar 2000) |
| random pattern flap | A flap in which the pedicle blood supply is derived randomly from the network of vessels in the area, rather than from a single longitudinal artery as in an axial pattern flap. (05 Mar 2000) |
| random sample | A group selected randomly, solely by chance. (12 Dec 1998) |
| random sampling | A selection of elements by a formal randomizing device for purposes of inference about a population of inference from that population in such a way that the probability of each possible outcome may be precisely specified in advance; the inferences are necessarily stochastic. (05 Mar 2000) |
| random walk | <cell biology> A description of the path followed by a cell or particle when there is no bias in movement. The direction of movement at any instant is not influenced by the direction of travel in the preceding period. If changes of direction are very frequent, then the displacement will be small, unless the speed is very great and the object will appear to vibrate on the spot. Although the behaviour of moving cells in a uniform environment can be described as a random walk in the long term, this is not true in the short term because of persistence. (18 Nov 1997) |
| random waves | Wave's in the electroencephalogram which occur paroxysmally and asynchronously. (05 Mar 2000) |
| moderator variable | A variable that interacts by virtue of being antecedent or intermediate in the causal pathway. (05 Mar 2000) |
| common variable immunodeficiency | Heterogeneous group of immunodeficiency syndromes characterised by hypogammaglobulinaemia of most isotypes, variable B-cell defects, and the presence of recurrent bacterial infections. (12 Dec 1998) |
| condenser, variable-focus | <microscopy> Essentially an Abbe condenser in which the upper lens element is fixed and the lower movable. The lower lens may be used to focus the illumination between the elements so that it emerges from the stationary lens as a large diameter parallel bundle. The field of low-power objectives may thus be filled without removing the top element. at the opposite extreme it can be adjusted to have a numerical aperture as high as 1.3. See: illumination, critical. (05 Aug 1998) |