Childbearing outside marriage in western Europe

Across most European states in recent decades there have been significant increases in childbearing outside marriage. This article examines the extent to which women have their first child in one of four settings: prior to any partnership; in their first cohabiting partnership; in first marriage; and after a first partnership. Temporal changes in these behaviours and variation according to background characteristics of the women are also examined. For the women who had a child outside any partnership, we examine the extent to which they go on to form partnerships and how long after the birth this happens. For those who had their first child within a cohabiting union, we examine the extent to which they marry and how long after the birth this occurs. Finally, we investigate whether children born within cohabiting unions that do and do not convert into marriages are more or less likely than those born within marriage to see their parents separate.     

Three-dimensional structure of motor molecules

Images, calculated from electron micrographs, show the three-dimensional structures of microtubules and tubulin sheets decorated stoichiometrically with motor protein molecules. Dimeric motor domains (heads) of kinesin and ncd, the kinesin-related protein that moves in the reverse direction, each appeared to bind to tubulin in the same way, by one of their two heads. The second heads show an interesting difference in position that seems to be related to the directions of movement of the two motors. X-ray crystallographic results showing the structures of kinesin and ncd to be very similar at atomic resolution, and homologous also to myosin, suggest that the two motor families may use mechanisms that have much in common. Nevertheless, myosins and kinesins differ kinetically. Also, whereas conformational changes in the myosin catalytic domain are amplified by a long lever arm that connects it to the stalk domain, kinesin and ncd do not appear to possess a structure with a similar function but may rely on biased diffusion in order to move along microtubules.     

Evolution of bacterial pathogenesis

The evolution of bacteria is associated with continuous generation of novel genetic variants. The major driving forces in this process are point mutations, genetic rearrangements, and horizontal gene transfer. A large number of human and animal bacterial pathogens have evolved the capacity to produce virulence factors that are directly involved in infection and disease. Additionally, many bacteria express resistance traits against antibiotics. Both virulence factors and resistance determinants are subject to intrastrain genetic and phenotypic variation. They are often encoded on unstable DNA regions. Thus, they can be readily transferred to bacteria of the same species or even to non-related prokaryotes. This review article focuses on the main mechanisms of bacterial microevolution responsible for the rapid emergence of variants with novel virulence and resistance properties. In addition, processes of macroevolution are described with special emphasis on gene transfer and fixation of adaptive mutations in the genome of pathogens.     

Mutations in CUBN, encoding the intrinsic factor-vitamin B12 receptor, cubilin, cause hereditary megaloblastic anaemia 1

Megaloblastic anaemia 1 (MGA1, OMIM 261100) is a rare, autosomal recessive disorder characterized by juvenile megaloblastic anaemia, as well as neurological symptoms that may be the only manifestations. At the cellular level, MGA1 is characterized by selective intestinal vitamin B12 (B12, cobalamin) malabsorption. MGA1 occurs worldwide, but its prevalence is higher in several Middle Eastern countries and Norway, and highest in Finland (0.8/100,000). We previously mapped the MGA1 locus by linkage analysis in Finnish and Norwegian families to a 6-cM region on chromosome 10p12.1 (ref. 8). A functional candidate gene encoding the intrinsic factor (IF)-B12 receptor, cubilin, was recently cloned; the human homologue, CUBN, was mapped to the same region. We have now refined the MGA1 region by linkage disequilibrium (LD) mapping, fine-mapped CUBN and identified two independent disease-specific CUBN mutations in 17 Finnish MGA1 families. Our genetic and molecular data indicate that mutations in CUBN cause MGA1.     

The complete family of genes encoding G proteins of Caenorhabditis elegans

Caenorhabditis elegans is the first animal whose genomic sequence has been determined. One of the new possibilities in post-sequence genetics is the analysis of complete gene families at once. We studied the family of heterotrimeric G proteins. C. elegans has 20 Galpha, 2 Gbeta and 2 Ggamma genes. There is 1 homologue of each of the 4 mammalian classes of Galpha genes, G(i)/G(o)alpha, G(s)alpha , G(q)alpha and G12alpha, and there are 16 new alpha genes. Although the conserved Galpha subunits are expressed in many neurons and muscle cells, GFP fusions indicate that 14 new Galpha genes are expressed almost exclusively in a small subset of the chemosensory neurons of C. elegans. We generated loss-of-function alleles using target-selected gene inactivation. None of the amphid-expressed genes are essential for viability, and only four show any detectable phenotype (chemotaxis defects), suggesting extensive functional redundancy. On the basis of functional analysis, the 20 genes encoding Galpha proteins can be divided into two groups: those that encode subunits affecting muscle activity (homologues of G(i)/G(o)alpha, G(s)alpha and G(q)), and those (14 new genes) that encode proteins most likely involved in perception.     

Myosins from plants

Molecular cloning and sequence analysis of myosin genes from Arabidopsis thaliana and electron microscopic observation of a myosin from characean alga have revealed that overall structure of plant unconventional myosins is similar to that of the class V myosins. These plant unconventional myosins have two heads, a coiled-coil tail of varied length and a globular tail piece at the end. The tail piece is probably a site for membrane interaction. Characean myosin is of special interest because it can translocate actin filaments at a velocity several times faster than muscle myosin, which must have evolved to support the quick movement of animals in the struggle for their lives.