| H0 | null hypothesis |
|---|---|
| H1 | alternative hypothesis |
| LNH | large number hypothesis |
| TRH | tension-reducing hypothesis; thyrotropin-releasing hormone |
| (3)H | hypothesis that |
|---|
| ara operon | <biochemistry, molecular biology> Operons involved in arabinose metabolism, especially. The araBAD operon of E. Coli.Two other ara operons are known in E. Coli. (18 Nov 1997) |
|---|---|
| rrna operon | Genetic loci which direct transcription and translation of ribosomal RNA in bacterial operons. They are designated rrnb, rrnc, rrnd, etc. According to the structural position of the transcription unit in the DNA sequence. (12 Dec 1998) |
| his operon | <molecular biology> An operon which governs the synthesis of the amino acid histidine out of ATP and phosphoribosyl pyrophosphate. The his operon was first observed in and described for the bacteria Salmonella typhinurium. (09 Oct 1997) |
| operon | <molecular biology> Groups of bacterial genes with a common promotor, that are controlled as a unit and produce mRNA as a single piece, polycistronic messenger. An operon consists of two or more structural genes, which usually code for proteins with related metabolic functions and associated control elements that regulate the transcription of the structural genes. The first described example was the lac operon. (18 Nov 1997) |
| Lac operon | Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. Coli. The lac operon was the first example of a group of genes under the control of an operator region to which a lactose repressor binds. When the bacteria are transferred to lactose containing medium, allolactose (which forms by transglycosylation when lactose is present in the cell) binds to the repressor, inhibits the binding of the repressor to the operator and allows transcription of mRNA for enzymes involved in galactose metabolism and transport across the membrane (_ galactosidase, galactoside permease and thiogalactoside transacetylase). (18 Nov 1997) |
| lactose operon | Group of adjacent and coordinately controlled genes concerned with the metabolism of lactose in E. Coli. The lac operon was the first example of a group of genes under the control of an operator region to which a lactose repressor binds. When the bacteria are transferred to lactose containing medium, allolactose (which forms by transglycosylation when lactose is present in the cell) binds to the repressor, inhibits the binding of the repressor to the operator and allows transcription of mRNA for enzymes involved in galactose metabolism and transport across the membrane (_ galactosidase, galactoside permease and thiogalactoside transacetylase). (18 Nov 1997) |
| adaptor hypothesis | A hypothesis, proposed by F.H.C. Crick, that an adaptor molecule must be present between the information-containing DNA and the protein being synthesised. (05 Mar 2000) |
| altered self hypothesis | The hypothesis that the T-cell receptor in MHC mediated phenomena recognises a syngeneic MHC Class I or Class II molecule after modification by a virus or certain chemicals. See: MHC restriction. (18 Nov 1997) |
| alternative hypothesis | In Neyman-Pearson testing of a hypothesis, the hypothesis or family of hypotheses about the numerical value of a parameter if and only if the null hypothesis is rejected as untenable. (05 Mar 2000) |
| autocrine hypothesis | That tumour cells containing viral oncogenes may have encoded a growth factor, normally produced by other cell types, and thereby produce the factor autonomously, leading to uncontrolled proliferation. (05 Mar 2000) |
| Avogadro's hypothesis | <physics> The hypothesis that equal volumes of two different gases at the same temperature and pressure contain the same number of molecules. (02 Jan 1998) |
| Bayesian hypothesis | An array of surmised values of a parameter to be severally explored in the light of a current set of data, with logical symmetry being preserved among all. The merits of each hypothesis entertained are based on quantity, the prior probability. The probability of the data conditional on the hypothesis is computed as the conditional probability for each; the product of the two for each hypothesis is the joint probability, and the ratio of each joint probability to the sum of all the joint probabilities is the posterior probability for that hypothesis. Unlike the Neyman-Pearson test of hypotheses, the answer is a statement about the hypothesis, not about the sample conditional on the hypothesis. No hypothesis is preferred or prevails by default. The procedure may be applied recursively any number of times, as the data becomes available. (05 Mar 2000) |
| Makeham's hypothesis | A development of Gompertz' hypothesis as to the force of mortality following some mathematical law. Makeham assumed that death was the consequence of two generally coexisting causes: 1) chance; 2) a deterioration or increased inability to withstand destruction. The first of these is constant, the second is an increasing geometrical progression. (05 Mar 2000) |
| gate-control hypothesis | A theory to explain the mechanism of pain; small fibre afferent stimuli, particularly pain, entering the substantia gelatinosa can be modulated by large fibre afferent stimuli and descending spinal pathways so that their transmission to ascending spinal pathways is blocked (gated). Synonym: gate-control hypothesis. (05 Mar 2000) |
| Gompertz' hypothesis | A theory that the force of mortality increases in geometrical progression, being based on the assumption that the average exhaustion of a person's power to avoid death is such that at the end of equal infinitely small intervals of time he loses equal proportions of the power to oppose destruction which he had at the commencement of each of these intervals. (05 Mar 2000) |
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