Two systematic RNAi screens in worms provide the first large-scale reverse genetic analyses of a multicellular organism.

How does gradual evolutionary change come up with a complex trait such as flying? One possible intermediate state for insects is surface-skimming, in which the insect's weight is borne by water, meaning that the wings must deal only with generating forward motion. A limited analysis suggested, however, that present-day surface skimmers were evolutionary latecomers, and had lost their previous ability to fly. In the November 21 Proceedings of the National Academy of Sciences, Thomas et al. analyz

In the 10 November Science Semino et al. use haplotypes from the non-recombining portion of the Y chromosome (NRY) of 1007 individuals to determine that ten lineages can account for 95% of European Y chromosomes (Science 2000, 290:1151-1155). Based on the geographic distribution of the haplotypes, and their age (estimated using the variation of associated microsatellites), Semino et al. identify two major haplotypes as belonging to Paleolithic peoples who migrated from the Iberian peninsula and

Guesses about the number of genes in the human genome vary wildly and may continue to do so even when the entire genome sequence is available. Computational methods for picking out exons that are scattered amongst vast introns yield both false positives and false negatives. This has prompted a Brazilian sequencing group to generate a quarter of a million open reading frame (ORF) expressed sequence tags (ORESTES), as they report in the November 7 Proceedings of the National Academy of Sciences (P

In just four years in the mid-fourteenth century, the medieval pandemic of 'Black Death' killed 17-28 million Europeans, or 30-40% of the total population. Further resurgences later in the century eliminated 90% of the households around Montpellier in southern France. It is in this region that Raoult et al. went searching for the causative agent of the Black Death. Although this agent has been presumed to be Yersinia pestis, the pattern of the disease's spread has led others to suggest alternati

In the November Nature Biotechnology Fiehn et al. offer an alternative to the profiling of messenger RNA and protein levels. They use gas chromatography coupled to mass spectrometry (GC/MS) to assay the relative levels of 326 small compounds from a plant leaf extract (Nat Biotech 2000, 18:1157-1161). A simple methanol extraction is followed by derivitization to increase metabolite stability and volatility. Approximately half of the chromatographed compounds can be identified based on retention t

The Bacillus subtilis SpoIIIE protein is required for DNA segregation during the asymmetric cell division that produces a mother cell and a pre-spore. In the 3 November Science, Bath et al. confirm that SpoIIIE is targeted to the leading edge of the septum that divides the two cells, and suggest that the protein pumps DNA into the pre-spore by tracking along DNA (Science 2000, 290:995-997). They find that SpoIIIE is a DNA-dependent ATPase that can introduce unconstrained supercoils into a DNA su

Analysis of four conserved proteins allows a better prediction of eukaryotic phylogeny.

Expressed sequence tags (ESTs) have given researchers a quick if dirty look at the coding potential of the human genome. But now in the November Nature Genetics, Penn et al. use microarray experiments to conclude that the human genome project will uncover many genes not previously discovered by EST sequencing (Nat Genet 2000, 26:315-318). They scan 350 Mb of finished and draft human sequence using three different gene-finding algorithms. Open reading frames (ORFs) predicted by at least two of th

The Caenorhabditis elegans lin-4 and let-7 genes encode small RNAs that bind to complementary sequences in the 3' untranslated region of various developmental genes. Both genes control developmental timing, with let-7 driving a transition from late larval to adult cell fates. In the 2 November Nature, Pasquinelli et al. report that homologs of let-7 (but not lin-4) are found in a wide range of bilaterian animals, including flies, abalone, sea urchins, sea squirts, zebrafish, frog and human (Natu

Blocking meiotic DNA replication in budding yeast prevents recombination initiation. This could indicate a direct coupling of the two processes, or the presence of a checkpoint system that detects incomplete replication and shuts down the formation of double-strand breaks (DSBs). In the 27 October Science, Borde et al. report that budding yeast cells defective for the replication checkpoint can progress through meiosis I in the absence of replication, but DSBs are still not formed (Science 2000,

Sequencing of the worm genome has allowed Hill et al. to design oligonucleotide arrays representing 18,791 (98%) of the predicted worm open reading frames (ORFs). In the 27 October Science, they report the use of these arrays to analyze transcripts from six developmentally staged worm populations from eggs to adults (Science 2000, 290:809-812). Only 56% of the ORFs are detected at least once, suggesting that others are missed because they are expressed at very low levels in specific tissues or u