Aggressiveness, nervousness, flightiness, gregariousness and overall disposition were evaluated in F2 Nellore-Angus embryo transfer calves (n = 443) from 13 full sib families and in half Bos indicus, half Bos taurus natural service calves (n = 259) from 4 paternal half sib families. Calves were born from 2003 to 2007, and evaluated shortly after weaning. Steers were evaluated shortly before slaughter for all 5 disposition traits and at slaughter for overall disposition. Heifers were evaluated for overall disposition at calving every year. Scores ranged from 1 to 9, with 1 being docile and 9 being unruly, except at calving where scores ranged from 1 to 5. Between sires for overall disposition, calves by 297J were lowest at weaning (2.83), before slaughter (2.84), and at slaughter (2.45) and second lowest in first calf heifers (2.27). Calves by 437J were highest at weaning (4.10), before slaughter (3.54), at slaughter (2.89) and in first calf heifers (3.10). Bulls had the lowest scores at weaning (2.54), although the number was small (n=10); females were the highest (4.01), and steers were intermediate (3.70). All 5 weaning traits were correlated (P < 0.05) with each other (0.73 to 0.96). The correlation of recipient disposition and weaning disposition of the calves was 0.12 (P < 0.05). Aggressiveness was not significantly correlated with other component traits before slaughter but was with overall disposition (0.19, P < 0.05). All other traits were significantly inter-correlated (0.60 to 0.97). Disposition at weaning was correlated with disposition before slaughter (0.43, P < 0.05). Slaughter disposition was correlated with weaning disposition (0.30, P < 0.001) and disposition before slaughter (0.27, P < 0.001). Disposition in first calf heifers was correlated with weaning disposition (0.34, P < 0.001) and disposition in second calf females (0.53, P < 0.0001). The results indicate that both genetics and recipient disposition affect calf disposition at weaning, calves with better dispositions at weaning have better dispositions later in life, and there is sufficient variability within and between these full sib and half sib families for use in QTL analysis for major genes for disposition in Nellore-Angus cross cattle.

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Thèses (M.A.)--Université de Sherbrooke (Canada), 2000. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

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Pharmacogenetics involves research into the hereditary basis for the different responses of individuals to drugs or other environmental pollutants. Several functional genetic polymorphisms of drug metabolising enzymes, transporters, receptors and other drug targets have been identified and characterised and these polymorphisms may be responsible for interethnic differences in drug disposition and disease risk. Few studies have focussed on ethnic African populations. Several genes that have known genetic polymorphism and have clinical implications for disease risk and/or treatment of patients were evaluated in a sample of the Ghanaian (West African) population. Catechol-O-methyltransferase (COMT) catalyses the 0-methylation of neurotransmitters, catechol hormones and drugs such as levodopa and methyldopa. Ethnic differences in COMT activity have been observed in several populations. Previous studies suggest that the homozygous low activity allele (COMT*L) is less common in individuals of African origin than Caucasians. COMT genotyping was performed using a mini-sequencing method in 195 healthy Ghanaians. The frequency of the homozygous low activity allele was 6%. In Caucasians it is 31%. This study provides confirmation that the low activity COMT allele is less common in individuals of African origin. This finding may be important clinically with regards to the treatment of many neuropsychiatric disorders and in the pathophysiology of various human disorders including oestrogen-induced cancers, Parkinson's disease, depression and hypertension. This thesis aimed to determine the allele frequency of therapeutically important genetic polymorphisms in an African (Ghanaian) population. The data was then compared to other ethnic populations. The marked racial and ethnic differences in the frequency of functional polymorphisms in these drug- and xenobiotic-metabolising enzymes, transporters, receptors and other drug targets shows that ethnic origin needs to be considered in studies aimed at discovering whether specific genotypes or phenotypes are associated with disease risk or drug toxicity. Genotyping prior to treatment may be essential, as 95% of the Ghanaian subjects genotyped had between one and four mutations in the therapeutically important genes analysed. Genotyping assays specific for predominant mutant alleles should be used in different ethnic groups.

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A thesis submitted to the Faculty of Humanities, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, 2017 / Powers theory is the view that some ontic or sparse properties are essentially powerful in the sense that they are “for” or “directed toward” certain manifestations. In this thesis, I consider in detail the idea that the nature of unmanifested dispositions generates serious difficulties for powers theory. I argue that extant arguments based on this idea do not succeed but also that a novel argument based on the idea does raise significant problems for powers theory and, especially, for dispositional essentialism – the version of powers theory on which some powers are fundamental natural properties. In the first two chapters, I argue that on the most charitable interpretation the most plausible extant arguments from unmanifested dispositions against powers theory collapse into a single basic argument. The putative problem that this argument raises for powers theory is that some powers stand in a relation with manifestations that do not actually exist. In chapter three, I develop an argument from unmanifested dispositions that does not depend on this idea. According to this argument, unmanifested dispositions commit the powers theorist to the problematic idea that entities that do not actually exist have a sort of ontological priority over entities that actually exist. In chapter four, I argue that the arguments discussed in the first three chapters are seriously undermined by the fact that the “directedness” of a power instance need involve only the possibility of that power instance’s token manifestation and not the token manifestation itself. In chapters five and six, I use Kit Fine’s conception of ontological dependence to reformulate the argument developed in chapter three so that it gets around this difficulty. I argue that this argument provides good grounds to think that the dispositional essentialist is committed to the claim that unrealised possibilities have a significant sort of explanatory priority over concrete reality. This result is problematic for the dispositional essentialist, as this claim is strongly counterintuitive, entails the falsity of significant forms of ontological naturalism, and is inconsistent with important parts of the standard motivation for dispositional essentialism. / XL2018