The Drosophila melanogaster Genetic Reference Panel

A major challenge of biology is understanding the relationship between molecular genetic variation and variation in quantitative traits, including fitness. This relationship determines our ability to predict phenotypes from genotypes and to understand how evolutionary forces shape variation within and between species. Previous efforts to dissect the genotype-phenotype map were based on incomplete genotypic information. Here, we describe the Drosophila melanogaster Genetic Reference Panel (DGRP), a community resource for analysis of population genomics and quantitative traits. The DGRP consists of fully sequenced inbred lines derived from a natural population. Population genomic analyses reveal reduced polymorphism in centromeric autosomal regions and the X chromosome, evidence for positive and negative selection, and rapid evolution of the X chromosome. Many variants in novel genes, most at low frequency, are associated with quantitative traits and explain a large fraction of the phenotypic variance. The DGRP facilitates genotype-phenotype mapping using the power of Drosophila genetics.     

Disposition of intra-articularly injected hydrocortisone acetate,hydrocortisone free alcohol and cortisone acetate in arthritis

Riassunto In pazienti affetti da artrite reumatoide viene iniettato cortisone acetato, idrocortisone acetato, o idrocortisone, nel cavo sinoviale artritico.La durata del riassorbimento di questi 17-idrossicorticoidi; la loro distribuzione nelle cellule e nel fluido articolare e nelle cellule del rivestimento sinoviale; le andamento del processo idrolitico dei composti acetati, studiati con mezzi chimici e cromatografici, si prestano a commenti utili ad interpretare la maggiore efficacia locale dell'idrocortisone.

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Supported by a grant from the Helen Augusta Parkhill Foundation.—Communication at the 8^th International Congress of Rheumatic Diseases, Geneva, August 1953.     

Frequent chromosomal translocations induced by DNA double-strand breaks

The faithful repair of DNA damage such as chromosomal double-strand breaks (DSBs) is crucial for genomic integrity. Aberrant repair of these lesions can result in chromosomal rearrangements, including translocations, which are associated with numerous tumours. Models predict that some translocations arise from DSB-induced recombination in differentiating lymphoid cell types or from aberrant repair of DNA damage induced by irradiation or other agents; however, a genetic system to study the aetiology of these events has been lacking. Here we use a mouse embryonic stem cell system to examine the role of DNA damage on the formation of translocations. We find that two DSBs, each on different chromosomes, are sufficient to promote frequent reciprocal translocations. The results are in striking contrast with interchromosomal repair of a single DSB in an analogous system in which translocations are not recovered. Thus, while interchromosomal DNA repair does not result in genome instability per se, the presence of two DSBs in a single cell can alter the spectrum of repair products that are recovered.     

The effect of pyridoxine and pyridoxal on the circulatory response of rats to microwave irradiation

Résumé L'administration intraveineuse de pyridoxine et pyridoxal (10 mg/kg) à des rats anesthésiés inhibe l'augmentation du rendement du cocur. En même temps, une hyperthermie est provoquée par l'irradiation du corps entier avec des ondes de longueur minime (2,450 Mc. c.w. 0.08/w/cm²). Cet effet peut être attribué à l'interaction de ces composés d'amines vasoactifs libérés pendant l'irradiation.     

Rotational breakup as the origin of small binary asteroids

Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular orbits. About 15 per cent of near-Earth and main-belt asteroids with diameters under 10 km have satellites. The mechanism that forms such similar binaries in these two dynamically different populations was hitherto unclear. Here we show that these binaries are created by the slow spinup of a 'rubble pile' asteroid by means of the thermal YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect. We find that mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative and the primary maintains a low equatorial elongation. The satellite forms mostly from material originating near the primary's surface and enters into a close, low-eccentricity orbit. The properties of binaries produced by our model match those currently observed in the small near-Earth and main-belt asteroid populations, including 1999 KW(4) (refs 3, 4).