Fertility assumptions for the 2002-based national population projections

One of the key components of national population projections is the assumed level of fertility, which determines the number of future births in the projections. Assumptions are made in terms of the average number of children women will have over their lifetime. For the 2002-based projections this average is assumed to ultimately be 1.75 for England and for Wales, 1.60 for Scotland, and 1.80 for Northern Ireland, leading to a United Kingdom assumption of 1.74. This article explains how these overall assumptions, which are the same as assumed in the 2000-based and interim 2001-based projections, are derived. It also explains why these levels are higher than current 'period' indicators of fertility. Finally, information on more detailed age specific fertility rates, and implications for family size distributions, is given.     

Higher qualifications,first-birth timing,and further childbearing in England and Wales

This article examines how strong the association is between the obtaining of higher educational qualifications and later entry to motherhood, and how these are associated with levels and pace of second and subsequent childbearing. Data from the ONS Longitudinal Study are used to estimate these associations for women born in England and Wales between 1954 and 1958. Average age of entry to motherhood is found to be five years later for women with higher qualifications than for those without. Increasing age of motherhood is always associated with a lower likelihood of going on to have another child, but the decline with age is less pronounced for women with a higher qualification. Moreover, for any given age of childbearing, mothers with a higher qualification are more likely than those without to have another child, and are more likely to do so quickly.     

The European dimension for the mouse genome mutagenesis program

The European Mouse Mutagenesis Consortium is the European initiative contributing to the international effort on functional annotation of the mouse genome. Its objectives are to establish and integrate mutagenesis platforms, gene expression resources, phenotyping units, storage and distribution centers and bioinformatics resources. The combined efforts will accelerate our understanding of gene function and of human health and disease.     

Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity

Postcopulatory sperm competition is a key aspect of sexual selection and is believed to drive the rapid evolution of both reproductive physiology and reproduction-related genes. It is well-established that mating behavior determines the intensity of sperm competition, with polyandry (i.e., female promiscuity) leading to fiercer sperm competition than monandry. Studies in mammals, particularly primates, showed that, owing to greater sperm competition, polyandrous taxa generally have physiological traits that make them better adapted for fertilization than monandrous species, including bigger testes, larger seminal vesicles, higher sperm counts, richer mitochondrial loading in sperm and more prominent semen coagulation. Here, we show that the degree of polyandry can also impact the dynamics of molecular evolution. Specifically, we show that the evolution of SEMG2, the gene encoding semenogelin II, a main structural component of semen coagulum, is accelerated in polyandrous primates relative to monandrous primates. Our study showcases the intimate relationship between sexual selection and the molecular evolution of reproductive genes.