| nucleotide pair | <molecular biology> Two nitrogenous bases (adenine and thymine or guanine and cytosine) held together by weak bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs. (09 Oct 1997) |
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| Abegg's rule | The tendency of the sum of the maximum positive and maximum negative valence of a particular element to equal 8; e.g., C may have a valence of +4 and -4, O of +6 and -2. Sometimes loosely stated as all atoms have the same number of valences, a consequence of the tendency of valence electron shells to be filled to 8. (05 Mar 2000) |
| American Law Institute rule | A test of criminal responsibility (1962): "a person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity either to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements of law." (05 Mar 2000) |
| astigmatism against the rule | Astigmatism when the greater curvature or refractive power is in the horizontal meridian. (05 Mar 2000) |
| astigmatism with the rule | Astigmatism when the greater curvature or refractive power is in the vertical meridian. (05 Mar 2000) |
| Gibb's phase rule | An expression of the relationships existing between systems in equilibrium: P + V = C + 2, where P is the number of phases, V the variance or degrees of freedom, and C the number of components; it also follows that the variance is, V = C + 2 -P. For H2O at its triple point, V = 1 + 2 -3 = 0, i.e., both temperature and pressure are fixed. Synonym: Gibb's phase rule. (05 Mar 2000) |
| Gloger's rule | The rule or observation that the skin of a warm-blooded animal species tends to become darker in colour towards warmer climates at lower altitudes or lower latitudes, and to become lighter in colour towards colder climates at higher altitudes or higher latitudes. (09 Oct 1997) |
| Goriaew's rule | Rarely used term for a rule of a blood counting field by which it is marked off in a series of squares, some of which are again subdivided into sixteen smaller ones. (05 Mar 2000) |
| Chargaff's rule | In DNA the number of adenine units equals the number of thymine units; likewise, the number of guanine units equals the number of cytosine units. (05 Mar 2000) |
| gt-ag rule | This is the observation that all introns in DNA begin with the nucleotides of GT(guanine, thymine) and end with the nucleotides AG (adenine, guanine). When the DNA is transcribed into RNA, the introns are removed from the RNA by a mechanism which recognises these beginning and ending nucleotides - in the RNA they would be CU (cytosine, uracil) and AC (adenine, cytosine). (09 Oct 1997) |
| Rolleston's rule | The ideal adult systolic blood pressure is 100 plus half the age, whereas the maximal physiologic pressure is 100 plus the age; of historical interest. (05 Mar 2000) |
| Meyer-Overton rule | <anaesthetics> Because inhalation agents act via the lipid-rich CNS cells, anaesthetic potency increases with lipid solubility. (05 Mar 2000) |
| phase rule | An expression of the relationships existing between systems in equilibrium: P + V = C + 2, where P is the number of phases, V the variance or degrees of freedom, and C the number of components; it also follows that the variance is, V = C + 2 -P. For H2O at its triple point, V = 1 + 2 -3 = 0, i.e., both temperature and pressure are fixed. Synonym: Gibb's phase rule. (05 Mar 2000) |
| rule | A statement of conditions, effects, or phenomena typically observed in agiven situation or process. (09 Oct 1997) |
| rule of bigeminy | Rule that a ventricular premature beat will follow the beat terminating a long cycle. Sudden prolongation of the ventricular cycle, by changing the refractoriness in the conduction system, causes a peripheral region of bidirectional block to become transiently unidirectional and thus opens potential pathways for reentry to occur. (05 Mar 2000) |