Minor inheritance inhibits the calibration of the 10Be production rate from the AD 1717 Val Ferret rock avalanche, European Alps

To calibrate the in situ 10Be production rate, we collected surface samples from nine large granitic boulders within the deposits of a rock avalanche that occurred in AD 1717 in the upper Ferret Valley, Mont Blanc Massif, Italy. The 10Be concentrations were extremely low and successfully measured within 10% analytical uncertainty or less. The concentrations vary from 4829 ± 448 to 5917 ± 476 at g−1. Using the historical age exposure time, we calculated the local and sea level-high latitude (i.e. ≥60°) cosmogenic 10Be spallogenic production rates. Depending on the scaling schemes, these vary between 4.60 ± 0.38 and 5.26 ± 0.43 at g−1 a−1. Although they correlate well with global values, our production rates are clearly higher than those from more recent calibration sites. We conclude that our 10Be production rate is a mean and an upper bound for production rates in the Massif region over the past 300 years. This rate is probably influenced by inheritance and will yield inaccurate (e.g. too young) exposure ages when applied to surface-exposure studies in the area. Other independently dated rock-avalanche deposits in the region that are approximately 103 years old could be considered as possible calibration sites.

pATOM36 mediates mitochondrial protein import and mitochondrial DNA inheritance

The multisubunit ATOM complex mediates import of essentially all proteins across the outer mitochondrial membrane in T. brucei. Moreover, an additional protein termed pATOM36, which is loosely associated with the ATOM complex, has been implicated in the import of only a subset of mitochondrial matrix proteins. Here we have investigated more precisely which role pATOM36 plays in mitochondrial protein import. RNAi mediated ablation of pATOM36 specifically depletes a subset of ATOM complex subunits and as a consequence results in the collapse of the ATOM complex as shown by Blue native PAGE. In addition, a SILAC-based global proteomic analysis of uninduced and induced pATOM36 RNAi cells together with in vitro import experiments suggest that pATOM36 might be a novel protein insertase acting on a subset of alpha-helically anchored mitochondrial outer membrane proteins. Identification of pATOM36 interaction partners by co-immunoprecipitation together with immunofluorescence analysis furthermore shows that unexpectedly a fraction of the protein is associated with the tripartite attachment complex (TAC). This complex is essential for proper inheritance of the mtDNA; also called kinetoplast or kDNA; as it forms a physical connection between the kDNA and the basal body of the single flagellum throughout the cell cycle. Thus, the presence of pATOM36 in the TAC provides an exciting link between mitochondrial protein import and kDNA inheritance.

Land Inheritance Rules: Theory and Cross-Cultural Analysis

This paper develops a general theory of land inheritance rules. We distinguish between two classes of rules: those that allow a testator discretion in disposing of his land (like a best-qualified rule), and those that constrain his choice (like primogeniture). The primary benefit of the latter is to prevent rent seeking by heirs, but the cost is that testators cannot make use of information about the relative abilities of his heirs to manage the land. We also account for the impact of scale economies in land use. We conclude by offering some empirical tests of the model using a cross-cultural sample of societies.

Customary land tenure, inheritance rules, and smallholder farmers in Malawi

Based on information derived from six villages in various parts of rural Malawi, this paper examines the interrelationship between smallholder strategies to obtain land on the one hand, and customary land tenure and inheritance rules on the other. The paper revealed that although the majority of land transactions followed customary land tenure systems and inheritance rules, in a good number of cases land transactions deviated from the basic rules. One factor behind such deviation was the unique personal relationships that were developed between original landholders and heirs. Another factor was the seemingly increasing cases of returning wives in patrilineal villages. Still another factor was the intensifying land scarcity that encouraged villagers to adopt strategies to obtain land from any source by any means. On the other hand, there were also some cases in which the same land-scarcity problem induced villagers to countercheck the practice of flexible land transfer to prevent their lineage land from being alienated to non-kin members. These facts suggest that, in a land scarce situation, an individual strategy to obtain land rights from any possible sources by deviating from customary rules may occasionally be in conflict with a lineage strategy to countercheck such tendency.

Marriage as women's old age insurance : evidence from migration and land inheritance practices in rural Tanzania

In a traditional system of exogamous and patrilocal marriage prevalent in much of Sub-Saharan Africa, when she marries, a rural woman typically leaves her kin to reside with her husband living outside her natal village. Since a village that allows a widow to inherit her late husband's land can provide her with old age security, single females living outside the village are more likely to marry into the village. Using a natural experimental setting, provided by the longitudinal household panel data drawn from rural Tanzania for the period from 1991 to 2004, during which several villages that initially banned a widow's land inheritance removed this discrimination, this study provides evidence in support of this view, whereby altering a customary land inheritance rules in a village in favor of widows increased the probability of males marrying in that village. This finding suggests that providing rural women with old age protection (e.g., insurance, livelihood protection) has remarkable spatial and temporal welfare effects by influencing their decision to marry.

Better than nothing? : dowry in the absence of the legal protection of women's inheritance rights

The practice of dowry is often thought to be the root cause of the unequal treatment of women in India. For women without inheritance rights, however, dowry may function as their only source of protection. Using a nationwide dataset and exploiting a natural experimental situation, this study explores the effects of dowry on women's empowerment in India, a society where women do not have inheritance rights. In such a society, dowry seems to enhance women's status in the marital household. The effects reverse when women have equal inheritance rights as their brothers. Empirical analysis suggests that the outright ban on dowry that ignores the context may not necessarily benefit women.

The yeast Cac1 protein is required for the stable inheritance of transcriptionally repressed chromatin at telomeres

Cac1p is a subunit of yeast chromatin assembly factor I (yCAF-I) that is thought to assemble nucleosomes containing diacetylated histones onto newly replicated DNA [Kaufman, P. D., Kobayashi, R. & Stillman, B. (1997) Genes Dev. 11, 345–357]. Although cac1Δ cells could establish and maintain transcriptional repression at telomeres, they displayed a reduced heritability of the repressed state. Single-cell analysis revealed that individual cac1Δ cells switch from transcriptionally “off” to transcriptionally “on” more often per cell cycle than wild-type cells. In addition, cac1Δ cells were defective for transcriptional silencing near internal tracts of C1–3A sequence, but they showed no defect in silencing at the silent mating type loci when analyzed by a reverse transcription–PCR assay. Despite the loss of transcriptional silencing at telomeres and internal C1–3A tracts, subtelomeric DNA was organized into nucleosomes that had all of the features characteristic of silent chromatin, such as hypoacetylation of histone H4 and protection from methylation by the Escherichia coli dam methylase. Thus, these features of silent chromatin are not sufficient for stable maintenance of a silent chromatin state. We propose that the inheritance of the transcriptionally repressed state requires the specific pattern of histone acetylation conferred by yCAF-I-mediated nucleosome assembly.

Mitochondrial Inheritance Is Delayed in Saccharomyces cerevisiae Cells Lacking the Serine/Threonine Phosphatase PTC1

In wild-type yeast mitochondrial inheritance occurs early in the cell cycle concomitant with bud emergence. Cells lacking the PTC1 gene initially produce buds without a mitochondrial compartment; however, these buds later receive part of the mitochondrial network from the mother cell. Thus, the loss of PTC1 causes a delay, but not a complete block, in mitochondrial transport. PTC1 encodes a serine/threonine phosphatase in the high-osmolarity glycerol response (HOG) pathway. The mitochondrial inheritance delay in the ptc1 mutant is not attributable to changes in intracellular glycerol concentrations or defects in the organization of the actin cytoskeleton. Moreover, epistasis experiments with ptc1Δ and mutations in HOG pathway kinases reveal that PTC1 is not acting through the HOG pathway to control the timing of mitochondrial inheritance. Instead, PTC1 may be acting either directly or through a different signaling pathway to affect the mitochondrial transport machinery in the cell. These studies indicate that the timing of mitochondrial transport in wild-type cells is genetically controlled and provide new evidence that mitochondrial inheritance does not depend on a physical link between the mitochondrial network and the incipient bud site.

Biparental Inheritance of γ-Tubulin during Human Fertilization: Molecular Reconstitution of Functional Zygotic Centrosomes in Inseminated Human Oocytes and in Cell-free Extracts Nucleated by Human Sperm

Human sperm centrosome reconstitution and the parental contributions to the zygotic centrosome are examined in mammalian zygotes and after exposure of spermatozoa to Xenopus laevis cell-free extracts. The presence and inheritance of the conserved centrosomal constituents γ-tubulin, centrin, and MPM-2 (which detects phosphorylated epitopes) are traced, as is the sperm microtubule-nucleating capability on reconstituted centrosomes. γ-Tubulin is biparentally inherited in humans (maternal >> than paternal): Western blots detect the presence of paternal γ-tubulin. Recruitment of maternal γ-tubulin to the sperm centrosome occurs after sperm incorporation in vivo or exposure to cell-free extract, especially after sperm “priming” induced by disulfide bond reduction. Centrin is found in the proximal sperm centrosomal region, demonstrates expected calcium sensitivity, but appears absent from the zygotic centrosome after sperm incorporation or exposure to extracts. Sperm centrosome phosphorylation is detected after exposure of primed sperm to egg extracts as well as during the early stages of sperm incorporation after fertilization. Finally, centrosome reconstitution in cell-free extracts permits sperm aster microtubule assembly in vitro. Collectively, these results support a model of a blended zygotic centrosome composed of maternal constituents attracted to an introduced paternal template after insemination.

A human model for multigenic inheritance: Phenotypic expression in Hirschsprung disease requires both the RET gene and a new 9q31 locus

Reduced penetrance in genetic disorders may be either dependent or independent of the genetic background of gene carriers. Hirschsprung disease (HSCR) demonstrates a complex pattern of inheritance with ≈50% of familial cases being heterozygous for mutations in the receptor tyrosine kinase RET. Even when identified, the penetrance of RET mutations is only 50–70%, gender-dependent, and varies with the extent of aganglionosis. We searched for additional susceptibility genes which, in conjunction with RET, lead to phenotypic expression by studying 12 multiplex HSCR families. Haplotype analysis and extensive mutation screening demonstrated three types of families: six families harboring severe RET mutations (group I); and the six remaining families, five of which are RET-linked families with no sequence alterations and one RET-unlinked family (group II). Although the presence of RET mutations in group I families is sufficient to explain HSCR inheritance, a genome scan reveals a new susceptibility locus on 9q31 exclusively in group II families. As such, the gene at 9q31 is a modifier of HSCR penetrance. These observations imply that identification of new susceptibility factors in a complex disease may depend on classification of families by mutational type at known susceptibility genes.

A first trial of retrospective collaboration for positional cloning in complex inheritance: Assay of the cytokine region on chromosome 5 by the Consortium on Asthma Genetics (COAG)

The central problem of complex inheritance is to map oligogenes for disease susceptibility, integrating linkage and association over samples that differ in several ways. Combination of evidence over multiple samples with 1,037 families supports loci contributing to asthma susceptibility in the cytokine region on 5q [maximum logarithm of odds (lod) = 2.61 near IL-4], but no evidence for atopy. The principal problems with retrospective collaboration on linkage appear to have been solved, providing far more information than a single study. A multipoint lod table evaluated at commonly agreed reference loci is required for both collaboration and metaanalysis, but variations in ascertainment, pedigree structure, phenotype definition, and marker selection are tolerated. These methods are invariant with statistical methods that increase the power of lods and are applicable to all diseases, motivating collaboration rather than competition. In contrast to linkage, positional cloning by allelic association has yet to be extended to multiple samples, a prerequisite for efficient combination with linkage and the greatest current challenge to genetic epidemiology.

Seeing properties of an invisible object: Feature inheritance and shine-through

We characterize a class of spatio-temporal illusions with two complementary properties. Firstly, if a vernier stimulus is flashed for a short time on a monitor and is followed immediately by a grating, the latter can express features of the vernier, such as its offset, its orientation, or its motion (feature inheritance). Yet the vernier stimulus itself remains perceptually invisible. Secondly, the vernier can be rendered visible by presenting gratings with a larger number of elements (shine-through). Under these conditions, subjects perceive two independent “objects” each carrying their own features. Transition between these two domains can be effected by subtle changes in the spatio-temporal layout of the grating. This should allow psychophysicists and electrophysiologists to investigate feature binding in a precise and quantitative manner.

Trials of the beta model for complex inheritance.

Theoretical advantages of nonparametric logarithm of odds to map polygenic diseases are supported by tests of the beta model that depends on a single logistic parameter and is the only model under which paternal and maternal transmissions to sibs of specified phenotypes are independent. Although it does not precisely describe recurrence risks in monozygous twins, the beta model has greater power to detect family resemblance or linkage than the more general delta model which describes the probability of 0, 1, or 2 alleles identical by descent (ibd) with two parameters. Available data on ibd in sibs are consistent with the beta model, but not with the equally parsimonious but less powerful gamma model that assumes a fixed probability of 1/2 for 1 allele ibd. Additivity of loci on the liability scale is not disproven. A simple equivalence extends the beta model to multipoint analysis.

Logarithm of odds (lods) for linkage in complex inheritance.

Lod scores provide a method to unify linkage tests based on identity by descent and identity in marker state while permitting selection of the most informative individuals through their disease-related phenotypes and markers in relatives. After parametric lods are reviewed, a nonparametric approach that depends on a single logistic parameter beta is introduced. Lods for parents tested or unknown are derived, multiple pairwise mapping is presented, and power is shown to be good even for moderately small values of beta. Comparison of parametric and nonparametric approaches (yet to be made) will provide for polygenes the efficiency and reliability that lod scores gave to mapping of major loci 40 years ago.

Uniparental inheritance of mitochondrial and chloroplast genes: mechanisms and evolution.

In nearly all eukaryotes, at least some individuals inherit mitochondrial and chloroplast genes from only one parent. There is no single mechanism of uniparental inheritance: organelle gene inheritance is blocked by a variety of mechanisms and at different stages of reproduction in different species. Frequent changes in the pattern of organelle gene inheritance during evolution suggest that it is subject to varying selective pressures. Organelle genes often fail to recombine even when inherited biparentally; consequently, their inheritance is asexual. Sexual reproduction is apparently less important for genes in organelles than for nuclear genes, probably because there are fewer of them. As a result organelle sex can be lost because of selection for special reproductive features such as oogamy or because uniparental inheritance reduces the spread of cytoplasmic parasites and selfish organelle DNA.