DNA polymerase-primase from embryos of Drosophila melanogaster. DNA primase subunits

The primase associated with the DNA polymerase-primase of Drosophila melanogaster fails to show enzymatic turnover. However, it does show turnover when dissociated from the intact polymerase-primase. Both forms of the enzyme can catalyze the synthesis of primers that are not complementary to the DNA template. Like the intact enzyme, the isolated primase synthesizes primers of a unique chain length; however, they are twice as long as those synthesized by the polymerase-primase. The activity of the primase separated from the polymerase-primase is similar in all other respects to the intact polymerase-primase.     

Optimising two-stage independent culling selection in tree and animal breeding

Summary Theory is given for a simple practical method of predicting gain from two-stage independent culling, where stage 1 of selection is for individual performance and stage 2 is for either progeny performance only, or an index combining individual and progeny performance. Expected gain is determined as a direct function of heritabilities, genetic correlations, selection intensities and progeny-testing capacity. Results show the effect these parameters can have on proportions selected at each stage and, if multiple selection criteria are used, traits selected for first. Methods are discussed in the context of tree and animal breeding, with an example taken from forestry.     

The Clinical and Biochemical Spectrum of Congenital Adrenal Hyperplasia Secondary to 21-Hydroxylase Deficiency

21-Hydroxylase Deficiency (21-OH Deficiency) represents the most common form of Congenital Adrenal Hyperplasia (CAH), a complex and heterogenous group of conditions, characterised by defects in one of the five enzymes involved in adrenal steroidogenesis. Defects in this steroidogenic enzyme, the product of the CYP21A2 gene, cause disruption in the pathway involved in cortisol and aldosterone production and consequently, the accumulation of their steroid precursors as well as a resulting adrenocorticotrophic hormone (ACTH)-driven overproduction of adrenal androgens. Treatment with glucocorticoid, with or without mineralocorticoid and salt replacement, is directed at preventing adrenal crises and ensuring normal childhood growth by alleviating hyperandrogenism. Conventionally, two clinical forms of 21-OH Deficiency are described - the classical form, separated into salt-wasting and simple-virilising phenotypes, and the non-classical form. They are differentiated by their hormonal profile, predominant clinical features and age of presentation. A greater understanding of the genotype-phenotype correlation supports the view that 21-OH Deficiency is a continuum of phenotypes as opposed to a number of distinct phenotypical entities. Significant advancements in technologies such as Tandem Mass Spectrometry (TMS) and improvements in gene analysis, such as complete PCR-based sequencing of the involved gene, have resulted in remarkable developments in the areas of diagnosis, treatment and treatment monitoring, neonatal screening, prenatal diagnosis and prenatal therapy.     

Climate change effects on animal and plant phylogenetic diversity in southern Africa

Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.     

Variation in the shoot calcium content of angiosperms

This study describes the variation in the mean relative shoot Ca content within the angiosperms at the ordinal level. Data were derived from studies in the literature in which the shoot Ca content of two or more species had been compared, and from a hydroponic experiment in which plants were selected to represent the relative number of species within each angiosperm order. Across all angiosperms, most of the variation in shoot Ca content occurred at and above the level of the order. Relative shoot Ca contents and variances correlated between literature and experimental data. In general, orders of commelinoid monocots had lower Ca contents than other monocot or eudicot orders. These results are used to illustrate how physiological and ecological hypotheses can be formulated using literature data.     

Intermittent wetting of soils at high temperature reduces survival of the take-all fungus

Two pot experiments using naturally infested soil and a range of watering regimes were conducted to study the possible effect of level and frequency of wetting of hot soil (to simulate the period between growing seasons in Western Australia) on inoculum of the take-all fungus (Gaeumannomyces graminis var.tritici). In combination with the high soil temperatures, all watering regimes reduced infectivity and propagule number of the take-all fungus, this reduction being absent in dry soils.