| upstream activation site | A DNA sequence that regulates transcription like an enhancer but does notwork if its located downstream from a promoter. (09 Oct 1997) |
|---|---|
| upstream | <molecular biology> Refers to nucleotide sequences that precede the codons specifying the mRNA or that precede (are on the 5' side of) the protein coding sequence. Also used of the early events in any process that involves sequential reactions. (18 Nov 1997) |
| attachment sites | <microbiology, molecular biology> Particular loci in both bacterial and phage DNA molecules at which phage DNA is integrated into the bacterial DNA by recombination between these sites. (12 Dec 1998) |
| binding sites | The reactive parts of a macromolecule that directly participate in its specific combination with another molecule. (12 Dec 1998) |
| binding sites, antibody | Local surface sites on antibodies which react with antigen determinant sites on antigens. They are formed from parts of the variable regions of the fab fragment of the immunoglobulin. (12 Dec 1998) |
| chromosome fragile sites | Heritable sensitive regions of chromosomes which show up in vitro as non-staining bands. They are associated with chromosome breakage and other aberrations, and, when located on sex chromosomes, they produce phenotypic abnormalities. No abnormal phenotype has been definitely identified with autosomal fragile sites, but some rare autosomal recessive disorders may be due to homozygosity for fragile sites. Fragile sites are designated by the letters "fra" followed by the designation for the specific chromosome and locus. (12 Dec 1998) |
| contact sites A | Developmentally regulated adhesion sites that appear on the ends of aggregation competent Dictyostelium discoideum at the stage when the starved cells begin to come together to form the grex. Originally detected by the use of Fab fragments of polyclonal antibodies, raised against aggregation competent cells and adsorbed against vegetative cells, to block adhesion in EDTA containing medium. (Cell cell adhesion mediated by contact sites A, unlike that mediated by contact sites B, is not divalent cation sensitive). The fact that a mutant deficient in csA behaves perfectly normally in culture is puzzling. (18 Nov 1997) |
| contact sites B | Developmentally regulated adhesion sites that appear on the ends of aggregation competent Dictyostelium discoideum at the stage when the starved cells begin to come together to form the grex. Originally detected by the use of Fab fragments of polyclonal antibodies, raised against aggregation competent cells and adsorbed against vegetative cells, to block adhesion in EDTA containing medium. (Cell cell adhesion mediated by contact sites A, unlike that mediated by contact sites B, is not divalent cation sensitive). The fact that a mutant deficient in csA behaves perfectly normally in culture is puzzling. (18 Nov 1997) |
| crohn disease: sites | <radiology> Oesophagus: rare, stomach (2-20%): granulomatous gastritis, pseudo-post Bilroth-I appearance, ramshorn sign, antral-duodenal fistula, duodenum (4-10%): almost always associated with gastric involvement, bulb and proximal half of duodenum, small bowel (80%): regional enteritis, terminal ileum (alone/in combination): 95%, jejunum/ileum: 15%, commonly associated with medial caecal defect, colon (22-55%): granulomatous colitis, particularly on the right side, transverse stripe sign: contrast within coarse mucosal folds, rectum (35-50%) see: Crohn disease (12 Dec 1998) |
| sequence tagged sites | Short, tagged tracts of DNA sequence that are used as landmarks in genome mapping. In most instances, 200 to 500 base pairs of sequence define a sequence tagged site (sts) that is operationally unique in the human genome (i.e., can be specifically detected by the polymerase chain reaction in the presence of all other genomic sequences). The overwhelming advantage of stss over mapping landmarks defined in other ways is that the means of testing for the presence of a particular sts can be completely described as information in a database. (12 Dec 1998) |
| sequence-tagged sites | Short stretches of DNA sequences that can be detected by use of the polymerase chain reaction. (05 Mar 2000) |
| immunologically privileged sites | Sites where allografts are not readily rejected, probably because these particular areas have poor lymphatic drainage. (05 Mar 2000) |
| activation | <radiobiology> Activation occurs when a particle interacts with an atomic nucleus, shifting the nucleus into an unstable state, and causing it to become radioactive. In fusion research, where deuterium-tritium is a common fuel mixture, the neutron released when (D + T) combine to form (4He + n) can activate the reactor structure. In this case the 4He is inert, the neutron sticks to another nucleus, and the neutron + nucleus reaction creates an actvation product. Sometimes called radioactivation. See: activation product, activation analysis. (09 Oct 1997) |
| activation analysis | <radiobiology> Method for identifying and measuring chemical elements in a sample of material. Sample is first made radioactive by bombardment with neutrons, charged particles, or gamma rays. Newly formed radioactive atoms in the sample then give off characteristic radiations (such as gamma rays) that tell what kinds of atoms are present, and how many. (09 Oct 1997) |
| activation energy | <chemistry> The amount of energy (expressed in joules) that is needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state. (06 May 1997) |