PubMed · 3662580
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G Murphy. 1987. Are intelligence tests outmoded?. https://doi.org/10.1136/adc.62.8.773
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Extreme halophilic archaea are saturated with salt and the intracellular electrolyte concentration exceeds that of the extracellular environment. Enzymes and other proteins from extreme halophilic archaea have been purified for many years and studied by biochemical and biophysical solution methodologies. They are active and stable at multimolar salt concentrations and denature below 2 to 3 M NaCl or KCl. Adaptation to these high concentrations of salt, genetic and evolutionary aspects, and the possibility of biotechnological applications are problems of considerable interest. Since the status of this fascinating field of research was reviewed in 1992, malate dehydrogenase from Haloarcula marismortui, now known to be a tetramer, was sequenced, its gene was cloned and expressed in active form, and its physical properties were redefined. A single mutation of Arg100 (in the enzyme active site) to Gln switched the enzyme specificity from malate to lactate dehydrogenase. Recent determination of its molecular structure by X-ray crystallography (O. Dym et al., in press) provides an exciting basis for the understanding of the structure and function of extreme halophilic enzymes. A major problem which so far has not been tackled in the study of extreme halophilic archaea is the understanding of protein nucleic acid interactions which are essential for the performance of biological function. Whereas the stability and activity of enzymes and other proteins can be modified to perform at high salt concentrations by use of currently known structural concepts, the existence of meaningful protein nucleic acid interactions in physiological concentrations of 4 to 5 M KCl constitutes an unsolved enigma worth intensive investigation.
A model of phenotypic assortative mating was developed for application in segregation analysis. The model assumed a constant spouse correlation across the range of a quantitative trait or the liability to a discrete trait. Four traits were analyzed to evaluate: 1) the feasibility of applying likelihood analysis to pedigree data in order to distinguish between assortative mating and shared environmental effects as the source of spouse correlation; and 2) the impact on segregation analysis of the failure to account for either assortative mating or shared environmental effects, as appropriate. Height ratio (the ratio of sitting to standing height) and eye color comprised the traits for which the observed spouse correlation reflected assortative mating; serum cholesterol and peptic ulcers (with genotypes defined by the ABO blood group) comprised the traits for which the observed spouse correlation reflected shared environmental effects. For all four traits the test statistics agreed with the known cause of spouse correlation; however, significance was not attained for height ratio or serum cholesterol. The ability to distinguish between the causes of spouse correlation in pedigree data presumably depends on trait and sample characteristics which remain to be delineated. Despite significant spouse correlation, its omission from the segregation analysis model did not undermine the inference of major locus inheritance for any of the four traits. However, the lack of an impact for these traits does not preclude an impact for other traits of ignoring the appropriate spouse correlation in segregation analysis.