Speciation can be seen as the establishment of reproductive barriers among species. Hybrid zones provide us with an ideal situation to study the process of speciation because the evolution of reproductive isolation is still in progress. Hybrids usually suffer reduced fitness (i.e. leading to post-zygotic isolation) although they may have higher or similar fitness as the parental species in some...

Female reproductive trait were studied in four pure breeds (the Finnsheep, Suffolk, Targhee and Minnesota 100), the F1 crosses between Finnsheep rams and females of the other three breeds and F2 and backcross ewes. Precocity of sexual development, defined as the percentage of ewe lambs lambing at 12 months of age, was measured in 709 ewe lambs in 4 years. Lambing and weaning rates were measured...

In this paper, interspecific crosses among Crambe abyssinica, Crambe hispanica, and Crambe kralikii were reported. In the C. hispanica x C. abyssinica (H x A) cross, 118 F1 hybrids were produced without embryo rescue, while 5 F1 hybrids were obtained with embryo rescue, when C. hispanica was used as the female parent. In the reciprocal cross (A x H), 232 hybrids were obtained without embryo res...

Genetic linkage analysis in the laboratory mouse identified chromosomal regions containing genes that contribute to cholesterol accumulation in the liver and plasma. Comparisons between five inbred strains of mice obtained from the Jackson Laboratory (DBA/2, AKR, C57BL/6, SJL, and 129P3) revealed a direct correlation between intestinal cholesterol absorption and susceptibility to diet-induced h...

Italian ryegrass is one of the most important temperate forage grasses on a global basis. Improvement of both dry matter yield and quality of herbage have been major objectives of pasture grass breeding over the last century. F1 and F2 progeny sets derived from controlled pair-crosses between selected Italian ryegrass genotypes have been evaluated for yield and nutritive quality under field con...

The relationship between expression of xenotropic virus and the development of autoimmunization was studied in the progeny of crosses between New Zealand Black (NZB) and SWR mice. The (F1 X SWR) and F2 progeny segregated into three phenotypes: high-virus, low-virus, and virus-negative; F1 and (F1 X NZB) progeny were always high-virus. Autoantibodies, immune deposit nephritis and lymphomas devel...

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...

We investigated the involvement of loci on the sex chromosomes in the hypertension of the spontaneously hypertensive rat (SHR) by studying male F1 and F2 generation rats derived from reciprocal crosses of SHR with Wistar-Kyoto (WKY) rats (cross 1: WKY female x SHR male; cross 2: SHR female x WKY male). At 16 weeks of age there was no significant difference in the blood pressures of F1 animals d...

To elucidate the mechanisms of thermal adaptation and acclimation in ectothermic aquatic organisms from differing climates, we used a common-garden experiment for thermal stress to investigate the heat shock response of redband trout (Oncorhynchus mykiss gairdneri) from desert and montane populations. Evidence for adaptation was observed as expression of heat shock genes in fish from the desert...