The injection of F1 hybrid animals with parental spleen or lymph node cells leads to the activation of specific parental lymphocytes which recognize major histocompatibility complex (MHC) 1 -coded antigens of the other parental haplotype expressed by the F1 host (1). Such recognition can result in graft-vs.-host (GVH) reactions which are frequently associated with depressed in vivo cell-mediate...

According to the Dobzhansky-Muller model, hybrid sterility is a consequence of the independent evolution of related taxa resulting in incompatible genomic interactions of their hybrids. The model implies that the incompatibilities evolve randomly, unless a particular gene or nongenic sequence diverges much faster than the rest of the genome. Here we propose that asynapsis of heterospecific chro...

Antigen-binding receptors on T lymphocytes and IgG antibodies with the same antigen-binding specificity as the T-cell receptors display shared or identical idiotypes. This was shown using a system where adult F1 hybrid rats between two inbred strains were inoculated with T lymphocytes from one parental strain. Such F1 hybrid rats produce antibodies directed against idiotypic determinants presen...

BACKGROUND Hybrid weakness, a phenomenon opposite to heterosis, refers to inferior growth and development in a hybrid relative to its pure-line parents. Little attention has been paid to the phenomenological or mechanistic aspect of hybrid weakness, probably due to its rare occurrence. METHODOLOGY/PRINCIPAL FINDINGS Here, using a set of interspecific triploid F1 hybrids between Oryza sativa, ...

Background: The consequences of hybridization vary depending on the fitness of hybrids and pure species plants. Herbivory and fungal infection may affect fitness and often differ in their effect on hybrid versus pure-species genotypes. Questions: Do herbivory and fungal infection rates differ between pure species and hybrids? What is the underlying genetic basis of resistance to herbivory and f...

Host genetic control of the incubation period of Creutzfeldt-Jakob disease (CJD) was studied using various inbred strains of mice, including B10 congenic strains. Various incubation periods were found in mice injected either intracerebrally or intraperitoneally with the Fukuoka 1 strain of the CJD agent; NZW/Sea and A/JJms had the shortest, and B10.AKM/Ola and C57BL/6J the longest, incubation p...

"Ecological" speciation occurs when reproductive isolation evolves as a consequence of divergent selection between populations exploiting different resources or environments. We tested this hypothesis of speciation in a young stickleback species pair by measuring the direct contribution of ecological selection pressures to hybrid fitness. The two species (limnetic and benthic) are strongly diff...

The genetic basis of hybrid male sterility in house mice is complex, highly polygenic, and strongly X linked. Previous work suggested that there might be interactions between the Mus musculus musculus X and the M. m. domesticus Y with a large negative effect on sperm head morphology in hybrid males with an F1 autosomal background. To test this, we introgressed the M. m. domesticus Y onto a M. m...

Hybrid sterility in the heterogametic sex is a common feature of speciation in animals. In house mice, the contribution of the Mus musculus musculus X chromosome to hybrid male sterility is large. It is not known, however, whether F1 male sterility is caused by X-Y or X-autosome incompatibilities or a combination of both. We investigated the contribution of the M. musculus domesticus Y chromoso...