Ph.D. - Genetics
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ItemThe population genetic structure of the North Fly River region of Papua and New Guinea([Honolulu], 1970)The major objectives of this study were population definition in terms of cultural and demographic parameters of genetic significance, with genetic characterization in terms of some gene and genotypic frequencies, and empirical application of some proposed models of population structure, including quantification of genetic microdifferentiation.
ItemQuantitative inheritance of immunological response in swine( 1977)Pigs were used as an animal model for studying the sources of variation in immunological response, under selected dose levels of immunization and at various stages during the development of immunity. Special emphasis was focused on the genetic component of the variation. Bovine serum albumin was selected as an antigen to inject pigs at the age of 28 days. Based on the preliminary trials, two dose levels of BSA were chosen, namely 5 and 50 mg. The kinetics of immune response were studied to decide the time for taking blood samples for the main study. Three blood samples were taken at 14, 21 and 42 days after the first immunization, each representing the primary response, Rp, secondary response, Rs, and peak response, Rm, respectively. A total of 802 pigs which were offspring of 18 purebred boars, each mated with six females, were used in the main study. Antigen binding capacity was used for measuring the antibody response. Data expressed as percent antigen bound was transformed by angle. No significant difference was found in the effect of sex, birth weight, weaning weight or pre-weaning daily gain on immune response. Pigs which received 5 mg of BSA gave consistently higher response than those receiving 50 mg of dose level in all three response measurements, i.e. Rp, Rs and Rm. The difference between the two dose levels and among litters in all responses were highly significant, but did not show any interaction between the dose level and litter. The intrarelationship of immune response measured at the three stages were found positively correlated. The difference among sires was found to be statistically significant in immune response under the dose of 5 mg of BSA except for the primary response. Variations among dams within sires were significant only in the primary response. For pigs treated with 50 mg of BSA, no sire difference in the peak response was detected at the 1% significant level but the difference existed at the 5% significant level. Significant difference was found among dams within sires. The genetic contribution to the early response could not be important. As variation of immune response in 50 mg of BSA would be expected to manifest mainly enviromnenta1 influences, this part of data was not used for estimation of genetic parameters. The genetic variance of the three immune responses, 29, 59 and 51 percent of the phenotypic variance, showed an important effect on the secondary and peak response.. The litter environment decreased in importance from 25% of the phenotypic variance in primary response to zero in the secondary and peak response. The individual environmental variance showed a stable variation among the three immune responses. The genetic correlations between the two adjacent stages of immune response, i.e. Rp and Rs, and Rs and Rm were considerably higher than that between Rp and Rm. Similar results were also found in the correlation measurements of individual environment and phenotypic measurement. The heritability obtained from sire and dam component combined for secondary and peak response were 0.51 ± 0.04 and 0.40 ± 0.04. The estimates were considered to be more precise than those calculated from other variance components, In conclusion, the mu1tigenic control of immune response was demonstrated in the present study.
ItemA cytogenetic study of early embryonic development in an animal model( 1977)Several cytogenetic studies of human spontaneous abortions have reported 50 percent to contain chromosomal anomalies. Earlier losses due to chromosomal abnormalities or other causes which are not recognized as abortions remain unknown. Due to extreme difficulty in collecting material from man, there is a definite need for a good animal model. Chromosome defects have been observed in preimplantation blastocysts and embryos of other mammalian species including mouse, rat, hamster, rabbit and pig. The present study was designed to cytogenetically analyze early embryonic development by recovering preimplantation blastocysts and by collecting embryos during the implantation period in pigs. Fifty-eight animals were cytogenetically analyzed at 10, 11, 12, 13, 16, 17, 18 and 19 days gestation. Using direct chromosome preparation, 338 blastocysts from thirty-one animals were analyzed. A variety of ploidies were observed in the same blastocyst ranging from 2N to 21N. Forty blastocysts from seven animals were cultured for 24 hours. A variety of ploidies were observed in the same blastocyst ranging from 2N to large numbers of "high-order" polyploids greater than 32N. Fifty percent of the preimp1antation blastocysts in the direct preparation were polyploid mosaics, while 9S percent of the blastocysts after 24-hour culture were polyploid mosaics. This mosaicism was most likely due to chromosome preparation of trophoblast giant cells. Five cases of chromosomally abnormal blastocysts included three triploids, one haploid, and one translocation mosaic. The frequency of blastocysts demonstrating chromosome abnormalities (1.48 percent) most likely represented an underestimate of spontaneously occurring abnormalities. Tae polyploid mosaics were not included in the abnormal estimate. Using direct chromosome preparation, 192 embryos from twenty animals were analyzed. Polyploidy was insignificant and only four chromosomally abnormal embryos were observed. All four were monosomic mosaics and represented 2.08 percent of embryos studied. The pooled estimate of mortality for blastocysts was 12.8 percent and that for embryos was 31.8 percent. These data suggest that a significant number of conceptuses were lost during the implantation process. The cytogenetic data failed to support the hypothesis that the increased mortality was due to chromosomally abnormal blastocysts failing to survive implantation. However, the frequency of abnormal blastocysts was most likely an underestimate due to the mixed population of trophoblast giant cells and embryonic disc cells in the blastocyst preparations. A direct comparison to anomalies observed in human spontaneous abortions would not be appropriate. However, the value of swine as an animal model for early embryonic development remains to be fully explored.