| sexual generation | Reproduction by conjugation, or the union of male and female cells, as opposed to asexual generation. (05 Mar 2000) |
|---|---|
| skipped generation | A phenomenon of pedigrees in which a gene is transmitted from one affected person to another through a phenotypically unaffected person, as by recessivity (especially for X-linked traits), epistasis, variable expressivity, or absence of an environmental challenge such as a toxin. Except at a crass phenotypic level (e.g., clinical or commercial) this term becomes progressively less useful as the mechanisms are elucidated. (05 Mar 2000) |
| spontaneous generation | The obsolete hypothesis that living organisms can originate from nonliving matter. (09 Oct 1997) |
| nonsexual generation | Reproduction by fission, gemmation, or in any other way without union of the male and female cell, or conjugation. See: parthenogenesis. Synonym: heterogenesis, nonsexual generation. (05 Mar 2000) |
| f-1 generation | <genetics> Filial-One generation. The first generation of offspring which results after mating or genetically crossing two types of parents with different genotypes or phenotypes. (The parents are known as the P generation.) (09 Oct 1997) |
| f-2 generation | <genetics> Filial-Two generation. The generation of offspring which results from mating or genetically crossing members of the F-1 generation to each other. Members of this generation are two generations removed from the original parent generation, or the P generation. (09 Oct 1997) |
| filial generation | The offspring of a genetically specified mating: first filial generation (symbol F1), the offspring of parents of contrasting genotypes; second filial generation (F2), the offspring of two F1 individuals; third filial generation (F3), fourth filial generation (F4), etc., the offspring in succeeding generation's of continued inbreeding of F1 descendents. (05 Mar 2000) |
| Abbe test plate | <equipment> A long, wedge-shaped coverslip about 0.20 mm thick at one end and 0.10 to 0.12 mm at the other end coated chemically with a silver film on which are ruled horizontal lines. at each variation in thickness of 0.01 mm there are vertical lines. By means of oblique illumination and by focusing on different portions of the plate, it is possible to determine the optimum coverslip thickness for any objective and also, for microscopes with drawtubes, the tube length for best objective performance. The approximate freedom from spherical and chromatic aberrations can also be estimated. Small isolated bits of silver near the edges of the lines form good objects for the star test (05 Aug 1998) |
| acetone test | A test for ketonuria; the suspected urine is shaken up with a few drops of sodium nitroprusside, and strong ammonia water is then gently poured over the mixture; if acetone is present, a magenta ring forms at the line of contact; tablets containing sodium nitroprusside and alkali are now more commonly used. (05 Mar 2000) |
| achievement test | A standardised test used to measure acquired learning, e.g., competence in a specific subject area such as reading or arithmetic, in contrast to an intelligence test which is a useful index of potential ability or learning. (05 Mar 2000) |
| acidified serum test | Lysis of the patient's red cells in acidified fresh serum, specific for paroxysmal nocturnal haemoglobinuria. Synonym: Ham's test. (05 Mar 2000) |
| acid loading test | <nephrology> This is a test used in the diagnosis of renal tubular acidosis. The patient takes ammonium chloride capsules for 3 days to acidify the blood (lower blood pH). A sample of the urine and the blood is then collected and the results are interpreted. (27 Sep 1997) |
| acid perfusion test | <gastroenterology, investigation> A test used to diagnosis gastrooesophageal reflux disease. This investigation requires that the patient swallow 3 tiny tubes into the stomach. A mixture of hydrochloric acid (like stomach acid) and saline are alternatively injected into the tubes. The patient then reports any symptoms they may have. Some patients may vomit. (13 Nov 1997) |
| acid phosphatase test for semen | A screening test for semen by determining acid phosphatase content; because seminal fluid contains high concentrations of acid phosphatase, while other body fluids and extraneous foreign materials have very low concentrations, high values of acid phosphatase on vaginal aspirate or lavage, or on wash fluid from stains, render positive identification of semen, even if the male is aspermic. (05 Mar 2000) |
| acid reflux test | A test to detect gastroesophageal reflux by monitoring oesophageal pH by an electrode in the distal oesophagus either basally or after acid is instilled into the stomach. (05 Mar 2000) |