hypothesis

A conjecture advanced for heuristic purposes, cast in a form that is amenable to confirmation or refutation by the conductance of definable experiments and the critical assembly of empiric data; not to be confused with assumption, postulation, or unfocused speculation. SEE ALSO: postulate, theory. [G. foundation, assumption fr. hypotithenai, to lay down]

- adaptor h. a h., proposed by F.H.C. Crick, that an adaptor molecule must be present between the information-containing DNA and the protein being synthesized.

- alternative h. in Neyman-Pearson testing of a h., the h. or family of hypotheses about the numerical value of a parameter if and only if the null h. is rejected as untenable.

- autocrine h. that tumor 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.

- Avogadro h. SYN: Avogadro law.

- Bayesian h. 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 h. entertained are based on quantity, the prior probability. The probability of the data conditional on the h. is computed as the conditional probability for each; the product of the two for each h. 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 h.. Unlike the Neyman-Pearson test of hypotheses, the answer is a statement about the h., not about the sample conditional on the h.. No h. is preferred or prevails by default. The procedure may be applied recursively any number of times, as the data becomes available.

- frustration-aggression h. the theory that frustration may lead to aggression, but that aggression is always the result of some form of frustration.

- gate-control h. SYN: gate-control theory.

- Goldie-Coldman h. a mathematic model that predicts that tumor cells mutate to a resistant phenotype at a rate dependent on their intrinsic genetic instability. The probability that a cancer would contain drug-resistant clones depends on the mutation rate and the size of the tumor. According to this h., even the smallest detectable cancers would contain at least 1 drug-resistant clone; therefore, the best chance of cure would be to use all effective chemotherapy drugs; in practice, this has meant using 2 different non–cross-resistant chemotherapy regimens in alternating cycles.

- Gompertz h. a theory that the force of mortality increases in geometrical progression, being based on the assumption that the average exhaustion of an individual's power to avoid death is such that at the end of equal infinitely small intervals of time the individual loses equal proportions of the power to oppose destruction that were available at the commencement of each of these intervals.

- insular h. obsolete theory of the origin of diabetes mellitus from destruction or loss of function of the islets of Langerhans in the pancreas.

- Knudsen h. an explanation for the bilateral (and earlier) occurrence of hereditary retinoblastoma; if one tumor suppressor gene is mutated by inheritance, only one somatic mutation is needed inactivate the other allele. In the sporadic form, 2 mutations, which inactivate each allele, are necessary.

- Lyon h. SYN: lyonization.

- Makeham h. a development of Gompertz h. 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.

- Michaelis-Menten h. a h. that a complex is formed between an enzyme and its substrate (also known as the O'Sullivan-Tompson h.), which complex then decomposes to yield free enzyme and the reaction products (also referred to as the Brown h.), the latter step being the rate-determining step for the overall rate of substrate-product conversion. SEE ALSO: Michaelis-Menten constant, Michaelis-Menten equation.

- mnemic h. the theory that stimuli or irritants leave definite traces (engrams) on the protoplasm of the animal, and when these stimuli are regularly repeated they induce a habit which persists after the stimuli cease. SYN: mnemic theory, mnemism, Semon-Hering theory.

- monoamine h. the classical theory of the neurochemical basis of depression linking it to a deficiency of at least one of three monoamine neurotransmitters, norepinephrine, serotonin, or dopamine.

- Neyman-Pearson statistical h. a formal conjecture about the numerical value of a parameter to be tested exclusively in the light of an immediate set of data without attention to prior knowledge or convictions and ignoring other sets of evidence treated in a similar fashion. The answer is a statement not about whether the h. is true but whether it is an acceptable explanation of the data or should be rejected in favor of another h..

- Norton-Simon h. h. that a tumor is composed of populations of faster-growing cells, which are sensitive to therapy, and slower-growing, more resistant cells. Since only therapy that completely eradicates all tumor cells will be curative, this is most likely to occur with sequential, non–cross-resistant regimens. The initial regimen must be effective enough to result in a low residual tumor burden and is followed by one or more non–cross-resistant treatments to eradicate the remainder of the cancer.

- null h. the statistical h. that one variable has no association with another variable or set of variables, or that two or more populations do not differ from each other; the statement that results do not differ from those that might be expected by the operation of chance alone; if rejected, it increases confidence in the h..

- sequence h. that the amino acid sequence of a protein is determined by a particular sequence of nucleotides (the cistron) in the DNA of the organism producing the protein.

- sliding filament h. the theory that the contracting muscle shortens because two sets of filaments slide past each other.

- Starling h. the principle that net filtration through capillary membranes is proportional to the transmembrane hydrostatic pressure difference minus the transmembrane oncotic pressure difference; although well established, it is called Starling h. to distinguish it from Starling law of the heart.

- upregulation/downregulation h. a theory of the neurochemical basis of depression (an elaboration of the monoamine h.) linking it to an increase in number (upregulation) of postsynaptic monoamine receptors, which are then effectively decreased in number (downregulation) as a result of antidepressant activity. SEE ALSO: monoamine h..

- wobble h. wobble base, wobble.

- zwitter h. that an amphoteric molecule ( e.g., an amino acid) has, at its isoelectric point, equal numbers of positive and negative charges, thus becoming a zwitterion.

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hy·poth·e·sis hī-'päth-ə-səs n, pl -e·ses -.sēz a proposition tentatively assumed in order to draw out its logical or empirical consequences and test its consistency with facts that are known or may be determined <it appears, then, to be a condition of the most genuinely scientific \hypothesis that it be...of such a nature as to be either proved or disproved by comparison with observed facts (J. S. Mill)>

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hy·poth·e·sis (hi-pothґə-sis) a supposition that appears to explain a group of phenomena and is advanced as a basis for further investigation; a proposition that is subject to proof or to an experimental or statistical test. See also theory.