The var genes of the malaria parasite Plasmodium falciparum encode the major variable parasite protein and are expressed in a mutually exclusive manner at the surface of an infected red blood cell. In the 26 October Nature, Freitas-Junior et al. report that Plasmodium uses nuclear architecture in a pathogen survival strategy (Nature 2000, 407:1018-1022). The sub-telomeric regions that contain the var genes are clustered together at the nuclear periphery, apparently allowing recombination at freq

Geneticists cut their teeth on conditions controlled by single loci. The harder task is to find the many loci that work together to control a single trait. In the 7 November Proceedings of the National Academy of Sciences Mott et al. demonstrate a new method for mapping these quantitative trait loci (QTL; Proc Natl Acad Sci USA 2000, published online before print). Previous methods all have their limits: family-based studies tend to be small and so can only do coarse mapping; population-based as

Humans are incredibly inefficient when it comes to reproduction. Fertile couples have only a 25% chance of achieving a viable pregnancy per menstrual cycle. Now, in the November Molecular Human Reproduction, Wells and Delhanty suggest that the low success rate may be explained by the high incidence of chromosomal abnormalities in early embryos, many of which never reach the stage of implantation (Mol Hum Reprod 2000, 6:1055-1062). In previous research, fluorescent in-situ hybridization (FISH) me

In the October 24 Proceedings of the National Academy of Sciences Rodin and Rodin propose that smoking leads to increased lung cancer not by causing more mutations, but by selecting for those mutations that do arise (Proc Natl Acad Sci USA 2000, 97:12244-12249). They take advantage of an increase in p53 mutational data in nonsmokers and find, for example, that the frequency of silent mutations in p53 is identical between smokers and non-smokers. In contrast, twice as many lung cancers from smoke

There is more variation in the rate of protein evolution than is expected by chance, although this variation is not caused by slower evolution of essential genes. In the 19 October Nature Williams and Hurst report that one determinant of evolution rates is gene position: the proteins of linked genes evolve at similar rates (Nature 2000, 407:900-903). The major cause of this phenomenon does not seem to be varying concentrations of mutation-sensitive CpG dinucleotides. The real cause may be the cl

The results reported by Vasquez et al. in the 20 October Science sound like a dream come true: the induction, after a simple injection of oligonucleotides into adult mice, of site-specific mutations (Science 2000, 290:530-533). The oligonucleotides are designed to form triple helices in polypurine regions with segments of mononucleotide repeats. The triple helix is thought to induce repair processes that often slip, producing short insertions or deletions near the site of the triple helix. Thus

Single nucleotide polymorphisms (SNPs) are sequence variants in which two alternate bases occur at one position. The SNP Consortium is developing a dense map of SNPs in the hope that certain variants can be associated with disease states. With hundreds of thousands of SNPs identified, the scoring of these SNPs in patient populations has become the limiting factor. Hirschhorn et al. provide a possible solution in the October 24 Proceedings of the National Academy of Sciences by making the existin

In the 19 October Nature Vreeland et al. report that the longevity record for bacteria has been smashed (Nature 2000, 407:897-900). The previous record holder was a Bacillus identified from the abdominal contents of a bee preserved in amber some 25 to 40 million years ago. The newly identified bacterium is also a Bacillus, but comes from a brine inclusion within a 250 million-year-old salt crystal. The crystal was found 569m below the surface, in the wall of an air-intake shaft of a waste isolat

In the 13 October Science Takizawa et al. use array analysis to identify a transmembrane protein that, combined with a septin barrier, may keep proteins in the daughter cells of budding yeast (Science 2000, 290:341-344). The messenger RNA for transcription factor Ash1p is already known to be transported to the bud tip of the daughter yeast cell by an actomyosin system; once the protein is translated in the daughter cell it represses mating-type switching. Takizawa et al. look for other transport

In the October 10 Proceedings of the National Academy of Sciences Gerton et al. use arrays to map hotspots and coldspots of meiotic recombination across the whole yeast genome (Proc Natl Acad Sci USA 2000, 97:11383-11390). They isolate DNA from sporulating cells that are mutant in rad50S, and therefore blocked with the recombination protein Spo11p covalently bound to DNA. The DNA fragments that are covalently linked to proteins (with Spo11p presumably predominant) are trapped using a glass filte

In the October 24 Proceedings of the National Academy of Sciences Butte et al. propose that relevance networks could provide a better way of analyzing genomic information than phylogenetic trees (Proc Natl Acad Sci USA 2000, 97, published online ahead of print). Phylogenetic trees derived from array experiments can only link a gene to one other gene, typically the one that is most strongly correlated in its expression pattern. In contrast, the method presented by Butte et al. can group any numbe

Selfish DNA may help to expand protein sequences, based on the discovery of DNA repeats inserted, in-frame, into 19 genes of an intracellular bacterium.