| excision repair | <molecular biology> Mechanism for the repair of environmental damage to one strand of DNA (loss of purines due to thermal fluctuations, formation of pyrimidine dimers by UV irradiation). The site of damage is recognised, excised by an endonuclease, the correct sequence is copied from the complementary strand by a polymerase and the ends of this correct sequence are joined to the rest of the strand by a ligase. The term is sometimes restricted to bacterial systems where the polymerase also acts as endonuclease. (11 Nov 1997) |
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| air-bone gap | The difference between the threshold for hearing acuity by bone conduction and by air conduction. (05 Mar 2000) |
| air-gap radiography | Chest radiography with a space (at least 10 inches) between the subject and film. Instead of using a grid, this method uses the geometry and X-ray absorption by the air to remove scattered radiation. (05 Mar 2000) |
| air-gap technique | Chest radiography performed using a space between the subject and film instead of a grid to absorb scattered radiation; usually requires a target-film distance of 10 feet. (05 Mar 2000) |
| anion gap | <biochemistry> The difference between the sum of the measured cations and anions in the plasma or serum calculated as follows: (Na + K) -(Cl + HCO3) = < 20 mmol/l. Elevated values may occur in diabetic or lactic acidosis; normal or low values occur in bicarbonate-losing metabolic acidoses. Synonym: cation-anion difference. (05 Mar 2000) |
| auscultatory gap | The period during which Korotkoff sounds indicating true systolic pressure fade away and reappear at a lower pressure point; responsible for errors made in recording falsely low systolic blood pressure, especially in hypertensive patients, of up to 25 mm Hg, and avoided by pumping the cuff 30 mm Hg beyond palpable systolic pressure. Synonym: silent gap. (05 Mar 2000) |
| Bochdalek's gap | A triangular area in the diaphragm near the lateral arcuate ligament that is devoid of muscle fibres; it is covered by pleura superiorly and by peritoneum inferiorly. Synonym: Bochdalek's gap, trigonum lumbocostale. (05 Mar 2000) |
| gap | A space in between two of the same objects, where part of a chain or object is missing, or where certain activities, processes, or events are lacking. A period of time characterised by a lack of activity, in between two events or within a continuous process. <genetics, molecular biology> A gap is a spot on a strand of DNA or RNA where a nucleotide or a segment of nucleotides is missing. (09 Oct 1997) |
| gap 1 | In the somatic cell cycle, the gap that follows mitosis and is followed by synthesis in preparation for the next cycle. (05 Mar 2000) |
| GAP-1 receptor tyrosine kinase | <enzyme> Similar to rasGTPase-activating proteins; inhibits signaling activity of let-60; amino acid sequence given in first source Registry number: EC 2.7.1.- Synonym: gap-1 gene product, gap-1 protein (26 Jun 1999) |
| gap 2 | In the somatic cell cycle, a pause between completion of synthesis and the onset of cell division. (05 Mar 2000) |
| gap-43 protein | A nervous tissue specific protein which is highly expressed in neurons during development and nerve regeneration. It has been implicated in neurite outgrowth, long-term potentiation, signal transduction, and neurotransmitter release. It is also a substrate of protein kinase c. (12 Dec 1998) |
| gap arthroplasty | The surgical correction of ankylosis by creating a space between the ankylosed part of a joint and the portion for which movement is desired. (05 Mar 2000) |
| gap gene | <molecular biology> Segmentation genes involved in specifying relatively coarse subdivisions of the embryo. They are expressed sequentially in development between egg polarity genes and pair rule genes. In Drosophila, there are at least three such genes, for example Kruppel. (18 Nov 1997) |
| gap junction | <cell biology> A junction between two cells consisting of many pores that allow the passage of molecules up to about 900D. Each pore is formed by an hexagonal array (connexon) of six transmembrane proteins (connexins) in each plasma membrane: when mated together the pores open, allowing communication and the interchange of metabolites between cells. Electrical synapses are gap junctions and metabolic cooperation depends upon the formation of gap junctions. (18 Nov 1997) |