Behavioral genetics: anxiety under interrogation.

Recent genetic mapping experiments in the mouse have made significant inroads into understanding the complex genetics of behavior and, in particular, anxiety.     

Behavioral genetics of Drosophila ananassae

Drosophila ananassae has a unique status among Drosophila species because of certain peculiarities in its genetic behavior. The most unusual feature of this species is its relatively high frequency of spontaneous male recombination. The results of studies on non-sexual behavior, such as phototactic responses, eclosion rhythm, and preferences for oviposition and pupation sites, lead us to suggest that this behavior is under polygenic control, with a substantial amount of additive genetic variation. Sexual isolation has been reported in D. ananassae with the degree of such isolation being stronger in isofemale lines than in natural populations. The significant variations seen in the mating propensity of several isofemale strains, inversion karyotypes and wild type strains, the diminishing effects of certain mutations on the sexual activity of males, and the positive responses to selection for high and low mating propensity point to a genetic control of sexual behavior in D. ananassae. Males contribute more to variation and thus are more subject to intrasexual selection than females. There is a positive correlation between sternopleural bristle number, mating propensity and fertility in D. ananassae. This correlation between morphometric traits and mating success suggests that larger flies are more successful in mating than smaller ones. There is also evidence for adaptive plasticity and a trade-off between longevity and productivity in D. ananassae. Rare, specific courtship song parameters that provide males with a mating advantage have also been reported in different geographic strains of D. ananassae. The remating behavior of males and females, sperm displacement, and the bi-directional selection for female remating speed indicate that post-mating behavior in this species may also be under genetic control. The occurrence of size assortative mating further indicates that there is size-dependent sexual selection in D. ananassae.     

Behavioral genetics: guanylyl cyclase prompts worms to party

When it comes to foraging, there are two types of worm in the world: those who enjoy a party, and those who prefer to dine alone. Two recent reports describe roles for guanylyl cyclase in the neuromolecular signaling systems that effect this natural behavioral dimorphism.     

Behavioral genetics in larval zebrafish: learning from the young

Deciphering the genetic code that determines how the vertebrate nervous system assembles into neural circuits that ultimately control behavior is a fascinating and challenging question in modern neurobiology. Because of the complexity of this problem, successful strategies require a simple yet focused experimental approach without limiting the scope of the discovery. Unbiased, large-scale forward genetic screens in invertebrate organisms have yielded great insight into the genetic regulation of neural circuit assembly and function. For many reasons, this highly successful approach has been difficult to recapitulate in the behavioral neuroscience field's classic vertebrate model organisms-rodents. Here, we discuss how larval zebrafish provide a promising model system to which we can apply the design of invertebrate behavior-based screens to reveal the genetic mechanisms critical for neural circuit assembly and function in vertebrates.     

The candidate gene approach in plant genetics: a review

The candidate gene (CG) approach has been applied in plant genetics in the past decade for the characterisation and cloning of Mendelian and quantitative trait loci (QTLs). It constitutes a complementary strategy to map-based cloning and insertional mutagenesis. The goal of this paper is to present an overview of CG analyses in plant genetics. CG analysis is based on the hypothesis that known-function genes (the candidate genes) could correspond to loci controlling traits of interest. CGs refer either to cloned genes presumed to affect a given trait (`functional CGs') or to genes suggested by their close proximity on linkage maps to loci controlling the trait (`positional CGs'). In plant genetics, the most common way to identify a CG is to look for map co-segregation between CGs and loci affecting the trait. Statistical association analyses between molecular polymorphisms of the CG and variation in the trait of interest have also been carried out in a few studies. The final validation of a CG will be provided through physiological analyses, genetic transformation and/or sexual complementation. Theoretical and practical applications of validated CGs in plant genetics and breeding are discussed.     

Behavioral genetics and neurogenetics and their development in Russia

The problems of behavioral genetics and neurogenetics and development of these fields in Russia are considered.     

Chemical genetics: ligand-based discovery of gene function

Chemical genetics is the study of gene-product function in a cellular or organismal context using exogenous ligands. In this approach, small molecules that bind directly to proteins are used to alter protein function, enabling a kinetic analysis of the in vivo consequences of these changes. Recent advances have strongly enhanced the power of exogenous ligands such that they can resemble genetic mutations in terms of their general applicability and target specificity. The growing sophistication of this approach raises the possibility of its application to any biological process.     

Matching genetics with oceanography: directional gene flow in a Mediterranean fish species

Genetic connectivity and geographic fragmentation are two opposing mechanisms determining the population structure of species. While the first homogenizes the genetic background across populations the second one allows their differentiation. Therefore, knowledge of processes affecting dispersal of marine organisms is crucial to understand their genetic distribution patterns and for the effective management of their populations. In this study, we use genetic analyses of eleven microsatellites in combination with oceanographic satellite and dispersal simulation data to determine distribution patterns for Serranus cabrilla, a ubiquitous demersal broadcast spawner, in the Mediterranean Sea. Pairwise population F_ST values ranged between ?0.003 and 0.135. Two genetically distinct clusters were identified, with a clear division located between the oceanographic discontinuities at the Ibiza Channel (IC) and the Almeria‐Oran Front (AOF), revealing an admixed population in between. The Balearic Front (BF) also appeared to dictate population structure. Directional gene flow on the Spanish coast was observed as S. cabrilla dispersed from west to east over the AOF, from north to south on the IC and from south of the IC towards the Balearic Islands. Correlations between genetic and oceanographic data were highly significant. Seasonal changes in current patterns and the relationship between ocean circulation patterns and spawning season may also play an important role in population structure around oceanographic fronts.     

Geneland: a computer package for landscape genetics

Geneland is a computer package that allows to make use of georeferenced individual multilocus genotypes for the inference of the number of populations and of the spatial location of genetic discontinuities between those populations. Main assumptions of the method are: (i) the number of populations is unknown and all values are considered a priori equally likely, (ii) populations are spread over areas given by a union of some polygons of unknown location in the spatial domain, (iii) Hardy–Weinberg equilibrium is assumed within each population and (iv) allele frequencies in each population are unknown and treated as random variable either following the so‐called Dirichlet model or Falush model. Different algorithms implemented in Geneland to perform inferences are first briefly presented. Then major running steps and outputs (i.e. histogram of number of populations and map of posterior probabilities of population membership) are illustrated from the analysis of a simulated data set, which was also produced by Geneland.     

The genetics of gene expression and gene mapping

A recent publication has shown that a significant portion of gene expression levels are under genetic control in different organisms, that there are hotspot regions in the genome that control the expression of many other genes, and how gene expression data can be used to localize genes that affect clinical traits.