Molecular evolution

Identifying genes of agronomic importance in maize by screening microsatellites for evidence of selection during domestication.Vigouroux, Y. et al. Proc. Natl Acad. Sci. USA 8 July 2002 (10.1073/pnas.112324299)

The domestication of cereals was accompanied by selection for improved agronomic and nutritional qualities; this paper reports a molecular genetic approach for identifying the genes underlying these important traits. Five hundred and one genes were screened for reduced microsatellite genetic diversity in domesticated maize compared with its wild ancestor. This work shows that evolutionarily important genes can be defined molecularly without previous knowledge of their phenotypic functions.

Mouse models

Removing the vertebrate-specific TBP N terminus disrupts placental β2m-dependent interactions with the maternal immune system.Hobbs, N. K. et al. Cell 110, 43–45 (2002)

Studying how modifications to the basic transcription machinery control complex gene-expression patterns led Hobbs et al. to an unexpected discovery. They generated mice that carried a TATA-binding protein (TBP) with a deletion of its vertebrate-specific amino-terminus. Most mice died in mid-gestation, but this effect could be rescued by wild-type placenta or if the mothers were severely immunocompromised, especially if they lacked β2-microglobulin (β2m). The authors propose that TBP transcriptionally regulates a β2m-dependent process involved in placental evasion of a maternal immune response.

Recombination

Reciprocal crossover asymmetry and meiotic drive in a human recombination hotspot.Jeffreys, A. J. & Neumann, R. Nature Genet. 31, 267–271 (2002)http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12089523&dopt=Abstract

Crossover clustering and rapid decay of linkage disequilibrium in the Xp/Yp pseudoautosomal gene SHOX.May, C. A. et al. Nature Genet. 31, 272–275 (2002)http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12089524&dopt=Abstract

In these papers, Alec Jeffrey's group analysed recombination events in human sperm DNA. In the first, the authors report a SNP at the centre of a recombination hot spot in the major histocompatibility complex that suppresses recombination by delaying crossover initiation. Crossovers in heterozygotes are consequently accompanied by gene conversion, resulting in the over-transmission of the recombination-suppressing allele. Computer simulations show that such alleles might become fixed by meiotic drive, leading to the extinction of human recombination hot spots. The accompanying paper looked at recombination patterns in the pseudoautosomal region PAR1. This high-resolution analysis unexpectedly shows that crossovers cluster into a recombination hot spot similar to autosomal hot spots, indicating that PAR1 might be useful for future studies of recombination.