Four experiments were conducted in an effort to explain further the genetics and physiology of sexual behavior in chickens and Japanese quail. The populations used in this research included lines that had undergone over 20 generations of divergent selection for high and low mating frequency and the random bred control population from which the selected lines originated. In the first experiment, fertility comparisons under natural and artificial mating situations were made over time among male chickens from the selected and control lines. Although there were highly significant differences among the lines for mating frequency, total fertility was similar among lines when mating was by either natural or artificial means. Significantly more days were needed to reach peak fertility when mating was by natural rather than artificial means. This difference may be attributed to male-female interactions whereby all females in a flock would not be fertilized on the same day in natural mating situations. This same reasoning could explain the significant differences noted between mating situations for duration of fertility. The second experiment examined the mode of inheritance of mating behavior and testosterone levels in chickens using the selected lines plus reciprocal crosses among these lines. No differences among mating combinations were found for circulating testosterone levels. In all cases, androgen titers appeared to be of a sufficient magnitude to influence mating behavior. Heterotic effects were found for mating behaviors in cross-pureline comparisons suggesting that nonadditive genetic variation influences the thresholds for mating in the fowl. Electroencephalographic effects of mating behavior of the selected lines were studied in the third experiment. There was an inverse relationship between number of peaks and voltages per peak, with differences in the number of peaks being significant among lines, implant locations and behavioral situations. Highly significant differences were found among lines for all voltage measurements with the control line having the highest voltage and the low mating line having the lowest voltage. These observations were discussed in the context of their effects on inhibitory and stimulatory mating centers. The genetics of mating frequency in male Japanese quail was studied in the fourth experiment utilizing replicated lines selected for high or low mating frequency and the randombred control line that served as the base population for the selected lines. Comparisons involved the purelines, F₁, F₂ and backcross generation progeny. The results indicate that the primary heritable variation for mating frequency in this species is primarily additive. Correlated responses of cloacal gland size and relative aggressiveness to selection for mating frequency are discussed in the context of alterations in physiological and behavioral responses. / Ph. D.

The association between selection for body weight and immune responsiveness was studied in Japanese quail and White Plymouth Rock chicken populations. Quail populations consisted of a randombred control (C) line and a line selected for high (HW) 28-day body weight. The chicken populations used were lines selected for high (HW) and low (LW) 56-day body weight, reciprocal Fi crosses (HL and LH), and F2 crosses of the Fi (HLHL and LHLH). Kinetics of primary and secondary antibody response to SRBC antigen was examined in Line C quail (Experiment 1). At most times post-primary inoculation (PPI), antibody titers were highest for antigen concentration 2.5%. The presence of MER antibodies was very low PPI, but increased following reinjection. Primary antibody response was then compared between C line and HW line of quail (Experiment 2). Antigen concentration 2.5% once again resulted in the highest titers. Line HW quail were less able to maintain high antibody titer levels to SRBC antigen than the randombred control line from which they originated. Mode of inheritance for immune responsiveness in selected populations of chickens and crosses between them was examined (Experiment 3). Additive genetic variation was important in the inheritance of both primary and secondary responses to this antigen. Reciprocal differences and heterosis of the F₁ crosses were also factors in the inheritance of secondary response. Kinetics of primary and secondary responses were evaluated in the parental weight lines and in lines of White Leghorn chickens divergently selected for antibody response to SRBC antigen. At all times PPI, line HA chickens had the highest antibody titers, while those from line LA consistently had the lowest titers. Lines HW and LW reacted similarly to line LA early in response, but showed higher peak levels later on. In both primary and secondary responses, the weight lines peaked at similar levels. Thereafter, line LW maintained a high antibody titer level to SRBC antigen than line HW. / Master of Science

Coat color and patterning phenotypes have been extensively studied as a model for advancing our understanding of the relationship between genetic and phenotypic variation. In this thesis, genes of relevance for pigment cell biology were investigated. The dissertation is divided in two parts. Forward genetics was used in the first part (Paper I and II) to identify the genes controlling the Silver and Sex-linked barring loci in chicken. In the second part, reverse genetics was employed to create a mouse line in which the PMEL17 protein is inactivated (Paper III). In Paper I, we report five mutations in SLC45A2 causing plumage color variants in both chicken and Japanese quail. Normal function of the SLC45A2 gene has previously been shown to be essential for the synthesis of both red/yellow pigment (pheomelanin) and brown/black pigment (eumelanin) in numerous species, including humans. The major discovery in this paper is the specific inhibition of pheomelanin in Silver chickens, whilst null mutations at this locus cause an almost complete absence of both pheomelanin and eumelanin. In Paper II, we report that Sex-linked barring in chickens is controlled by the CDKN2A/B tumor suppressor locus. The locus encodes two proteins, INK4B and ARF. The genetic analysis indicates that missense mutations in ARF or mutations in the promoter region of the ARF transcript are causing Sex-linked barring. In previous studies, mutations inactivating the CDKN2A/B tumor suppressor locus, have been shown to be responsible for familiar forms of human melanoma. Here we propose that these mutations in chicken CDKN2A/B cause the premature cell death of melanocytes as opposed to the cell proliferation and tumor growth associated with loss-of-function alleles in humans. In Paper III, we created a mouse line in which the PMEL17 protein is inactivated. Missense mutations in the gene encoding PMEL17 have previously been shown to be associated with reduced levels of eumelanin in epidermal tissues in several vertebrate species. The knockout mice are viable, fertile, and display no obvious developmental defects. The eumelanosomes within the melanocytes of these mice are spherical in contrast to the cigar-like shaped eumelanosomes present in wild-type animals. PMEL17 protein inactivation has only a subtle diluting effect on the coat color phenotype in four different genetic backgrounds. This suggests that other previously described alleles in vertebrates with more striking effects on pigmentation are dominant-negative mutations.

Made available in DSpace on 2014-07-29T15:07:46Z (GMT). No. of bitstreams: 1 Dissertacao Natali Gomes.pdf: 283005 bytes, checksum: 7137fd56067887481a4cc645f8148b81 (MD5) Previous issue date: 2008-03-28 / It was the objective of this study to evaluate the performance and reproductive parameters of different genetic groups of japanese quails between six and 26 weeks of age. There were used 384 japanese quails, assigned according to the experimental design (ramdomized blocks), considering the initial live weight of the birds as blocks in the beginning of the experiment. The treatments were three genetic groups with eight replicates, in a total of 48 experimental units with eight birds in each experimental unit (two males and six female). The birds were fed rations according to recommendations of NRC (1994), having soybean meal and ground corn as the main components. The variables of performance were studied every 14 days and three incubation trials were done with 15, 24 and 33 weeks of age. For the statistical analysis the proc GLM of SAS software was used and the means were compared by the t Student test. In each incubation study the completely ramdomized blocks experimental design was used, considering the incubating machines as blocks, with 70 replicates per treatment and one egg as the experimental unit. The parameters evaluated were the egg weight, hatchability, chick weight at hatching, weight loss and weight after six hours of fasting. The results were submitted to variance analysis and the means compared by the t Student test (5% of probability). The genetic groups presented differences among each other for the live body weight in the beginning of production, age at 50% of of productiontwere different to body weight at the beggining and age at 50% of production, where the commercial parent line obtained the best performance. The parameters peak persistence, eggs production, feed intake, viability and beak behavior did not present differences among the genetic groups. The live body weight influenced the egg weight. In the incubation trials the commercial parent line presented more weight of the incubating egg and more weight of the chicks at hatching. It was concluded in the present study that there are statistical differences on the performance and incubating parameters among genetic groups of japanese quails. / O objetivo deste estudo foi avaliar o desempenho e parâmetros reprodutivos de diferentes grupos genéticos de codornas japonesas entre seis e 26 semanas de idade. Foram utilizadas 384 codornas japonesas, distribuídas de acordo com delineamento experimental em blocos casualizados, considerando como blocos os pesos das aves no início do experimento. Os tratamentos estudados foram três grupos genéticos, com oito repetições, totalizando 48 parcelas com oito aves cada (dois machos e seis fêmeas). As aves receberam rações formuladas a partir de recomendações contidas no NRC (1994) tendo como base farelo de soja e milho moído. As variáveis de desempenho foram estudadas a cada período de 14 dias e foram realizados três ensaios de incubação, com 15, 24 e 33 semanas de idade. Para a análise estatística utilizou-se o procedimento GLM do programa SAS e as médias comparadas pelo teste t de Student. Em cada ensaio de incubação, foi adotado o delineamento experimental em blocos casualizados, sendo considerados blocos as incubadoras, com 70 repetições por tratamento, sendo considerado um ovo a parcela. As variáveis estudadas foram peso do ovo, eclodibilidade, peso ao nascer, perda de peso e peso no alojamento. Os resultados foram submetidos à análise de variância e as médias comparadas pelo teste t de Student (5% de probabilidade). As linhagens apresentaram diferenças entre si para peso ao início de produção e idade aos 50% de produção, sendo que a linhagem comercial apresentou os melhores resultados. Para as variáveis persistência de pico, produção de ovos, consumo de ração, viabilidade e comportamento de bicagem não foram observadas diferenças entre as linhagens. O peso das aves influenciou o peso do ovo. Nos ensaios de incubação, a linhagem comercial apresentou maior peso de ovo incubável e maior peso ao nascer das codorninhas. Conclui-se no presente estudo que há diferenças significativas para desempenho e parâmetros de incubação entre as linhagens de codornas japonesas estudadas.