Clonal expansion of isolated precursors to helper T cells was induced in limiting dilution cultures of keyhole limpet hemocyanin (KLH)-primed F1 hybrid lymph node cells. Progeny of each isolated precursor was tested for helper activity by transfer to independent cultures with hapten-primed B cells of either parental or F1 hybrid origin. The major histocompatibility complex (MHC) restriction spe...

Anemone coronaria L. and Ranunculus asiaticus L. both belong to the Ranunculaceae, a large plant family with many ornamentals of horticultural importance. There are considerable differences between these species leaves, flower morphology and flower colour therefore intergeneric crosses between the species might result in new interesting hybrids. Crosses between Anemone coronaria L. and Ranuncul...

Drosophila mojavensis from the Sonora region and Baja California show asymmetrical sexual isolation in the laboratory: males from Sonora mate equally frequently with Sonora and Baja females, while the mating success of Baja males with Sonora females is reduced. This failure has been localized to three separate behavioral landmarks occurring during courtship. Genetic analysis was conducted using...

The F1 hybrids of NZB and several normal mouse strains are known to produce less anti-erythrocyte (Coombs) autoantibody and develop a milder hemolytic anemia than their NZB parents. We have found that serum from some (NZB x CBA)F1 mice agglutinated erythrocytes from certain Coombs-positive NZB mice, often in extremely high titer, whereas other (CBA x NZB)F1 sera agglutinated erythrocytes from d...

The utilization of heterosis in rice, maize and rapeseed has revolutionized crop production. Although elite hybrid cultivars are mainly derived from the F1 crosses between two groups of parents, named NCII mating design, little has been known about the methodology of how interacted effects influence quantitative trait performance in the population. To bridge genetic analysis with hybrid breedin...

BACKGROUND AND AIMS Arachis batizocoi is a wild relative of cultivated peanut (A. hypogaea), an allotetraploid with an AABB genome. Arachis batizocoi was once considered the ancestral donor of the peanut B genome, but cytogenetics and DNA phylogenies have indicated a new genome classification, 'K'. These observations seem inconsistent with genetic studies and breeding that have shown that A. ba...

Atlantic herring, Clupea harengus, have complex population structures. Mixing of populations is known, but the extent of connectivity is still unclear. Phenotypic plasticity results in divergent phenotypes in response to environmental factors. A marked salinity gradient occurs from Atlantic Ocean (salinity 35) into the Baltic Sea (salinity range 2-12). Herring from both habitats display phenoty...

N the first paper of this series (STEBBINS, VALENCIA and VALENCIA I 1946a) two different natural hybrids between Elymus glaucus and Sitanion jubatum were described. Both were intermediate between their parents and were completely sterile. They nevertheless had essentially normal meiosis, with the chromosomes forming 14 bivalents or occasionally 13 bivalents and 2 univalents at first metaphase. ...

Quantitative absorption with specific anti-H-2 sera has shown that the H-2Kb and H-2Dd antigens coded by the B10.A(5R) haplotype are expressed in about fourfold lower amount on the spleen cells of [B10.A(5R) X B10.A(2R)]F1 hybrids than on parental B10.A(5R) cells. In contrast, the H-2Kk and H-2Db antigens of B10.A(2R) are expressed equally on parental and F1 cells. These quantitative difference...

The deleterious consequences of inbreeding have been well documented. There are, however, few empirical studies that have examined the consequences of restoring heterozygosity and hence the fitness of inbred populations by conducting interpopulation crosses and measuring the performance of later-generation hybrids under field conditions. We conducted interpopulation crosses of 100 m to 2000 km,...