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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

The Effects of Losing Sex on Genetic Variation in Oenothera (Onagraceae)

Godfrey, Ryan 2014 (has links)
Theory predicts that sexual reproduction confers an advantage over asexual reproduction due to the generation and maintenance of genetic variation afforded by the processes of recombination and segregation. However, this prediction has rarely been empirically tested. Oenothera is a flowering plant genus whose evolutionary history is punctuated with numerous transitions from sexual reproduction to a form of functionally asexual reproduction known as Permanent Translocation Heterozygosity (PTH). In Ch. 2, a greenhouse experiment examined patterns of phenotypic and genetic variation within and between populations across eight Oenothera species, representing four independent transitions to PTH. I found some evidence for a decrease in heritability and an increase in population differentiation in phenotypic traits associated with the loss of sex. Ch. 3 explored the possibility that rare outcrossing events represent a mechanism for the maintenance of variation in a PTH species. Analysis of microsatellite markers showed evidence for extremely low rates of outcrossing in natural populations (< 1%) of O. biennis, a PTH species.
22

Correlations between unexplained infertility and single nucleotide polymorphism in the genes of leukemia inhibitory factor receptor and gp130

Malki, Marwa 2010 (has links)

About 30 % of all infertile couples suffer from infertility of an unexplained cause. Leukemia inhibitory factor (LIF) is a glycoprotein produced by the endometrium and is an important cytokine in the implantation process. LIF exerts its biological functions through heterodimerization of its two receptors: LIF receptor (LIFR) and gp130. Point mutations in the LIF gene have been associated with female infertility. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in the genes of LIFR and gp130 could cause reduced fertility in women. To this end, 115 samples from women diagnosed with unexplained infertility and 191 samples from fertile women were studied. Three SNPs in the gp130 gene and two SNPs in the LIFR gene were analyzed using real-time PCR. One significant difference and a tendency to difference were detected in the gp130 gene for women with unexplained infertility. There were no differences in the LIFR gene variations. In conclusion, polymorphisms in gp130, and thereby disturbances in the LIF pathway, could be one cause for infertility in women diagnosed with unexplained infertility.

23

Correlations between unexplained infertility and single nucleotide polymorphism in the genes of leukemia inhibitory factor receptor and gp130

Malki, Marwa 2010 (has links)
About 30 % of all infertile couples suffer from infertility of an unexplained cause. Leukemia inhibitory factor (LIF) is a glycoprotein produced by the endometrium and is an important cytokine in the implantation process. LIF exerts its biological functions through heterodimerization of its two receptors: LIF receptor (LIFR) and gp130. Point mutations in the LIF gene have been associated with female infertility. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in the genes of LIFR and gp130 could cause reduced fertility in women. To this end, 115 samples from women diagnosed with unexplained infertility and 191 samples from fertile women were studied. Three SNPs in the gp130 gene and two SNPs in the LIFR gene were analyzed using real-time PCR. One significant difference and a tendency to difference were detected in the gp130 gene for women with unexplained infertility. There were no differences in the LIFR gene variations. In conclusion, polymorphisms in gp130, and thereby disturbances in the LIF pathway, could be one cause for infertility in women diagnosed with unexplained infertility.
24

The Effects of Losing Sex on Genetic Variation in Oenothera (Onagraceae)

Godfrey, Ryan 2014 (has links)
Theory predicts that sexual reproduction confers an advantage over asexual reproduction due to the generation and maintenance of genetic variation afforded by the processes of recombination and segregation. However, this prediction has rarely been empirically tested. Oenothera is a flowering plant genus whose evolutionary history is punctuated with numerous transitions from sexual reproduction to a form of functionally asexual reproduction known as Permanent Translocation Heterozygosity (PTH). In Ch. 2, a greenhouse experiment examined patterns of phenotypic and genetic variation within and between populations across eight Oenothera species, representing four independent transitions to PTH. I found some evidence for a decrease in heritability and an increase in population differentiation in phenotypic traits associated with the loss of sex. Ch. 3 explored the possibility that rare outcrossing events represent a mechanism for the maintenance of variation in a PTH species. Analysis of microsatellite markers showed evidence for extremely low rates of outcrossing in natural populations (< 1%) of O. biennis, a PTH species.
25

High throughput genotyping of single nucleotide polymorphisms in the Plasmodium falciparum dhfr and dhps genes by asymmetric PCR and melt-curve analysis

Cruz, Rochelle Unknown Date
No description available.
26

Molecular Typing of Giardia lamblia in Humans and Dogs and Evidence for Sexual Recombination

Cooper, Margarethe 2006 (has links)
Giardia lamblia is a eukaryotic parasite that causes diarrhea in humans worldwide. Diarrheal diseases cause stunting and mental retardation in children in developing nations, therefore it is important to understand the molecular epidemiology of G. lamblia. Compounding this, it is not clear if companion animals such as dogs contribute to infections in humans through zoonotic transmission. The genotypes of G. lamblia that have been found in humans are A1, A2 and B, while those in dogs have been on rare occasions all three human genotypes, but largely C and D, which have only been reported in dogs and appear to be species-specific. The molecular epidemiology of G. lamblia in humans and dogs was assessed in an endemic region of Lima, Peru. With one exception, dogs were found to harbor the C and D dog genotypes of G. lamblia. A single family dog was found to harbor a human genotype of G. lamblia. A2 and B genotypes of G. lamblia, but not A1, were found in humans in the endemic region. Previous literature reported that A2 and B typing within genotype tools were available, however the A2 samples from the endemic region could not be distinguished from one another through nucleotide polymorphism sequence analysis. A molecular typing technique was developed to type A2 samples. The extensive sequence analysis performed on two chromosomes of G. lamblia, yielded different phylogenetic tree groupings for the same samples. This lead to algorithmic analysis, which demonstrated a significantly high probability that meiotic recombination is occurring in the A2 samples of G. lamblia. As G. lamblia is largely believed to be asexual, the conclusion of doctoral research performed in this study yielded controversial, yet significant evidence that sex in G. lamblia A2 genotype samples is indeed occurring.
27

Genetic genealogy and epidemiology of Francisella

Svensson, Kerstin 2009 (has links)
This thesis is about analyzing genetic differences among isolates of Francisella tularensis – the tularemia-causing bacterium. To elucidate how these bacterial isolates are related, and their geographical and genetic origins, I have developed typing assays for Francisella and used them to study the epidemiology of tularemia. Tularemia is an infectious disease of humans and other mammals found throughout the Northern Hemisphere. The severity of the disease depends on the type of F. tularensis causing the infection. In Sweden, as in other countries of Europe and Eurasia, tularemia is caused by F. tularensis subsp. holarctica, while other varieties of the bacterium occur in Middle Asia and North America. It is important to identify a tularemia infection promptly in order to initiate the correct antibiotic treatment. A rapid identification of the causative F. tularensis variety gives additional clinical information. In recent years, several genomes of various Francisella strains have been sequenced, and in this thesis, I have utilized these genomes to identify genetic markers. In studies reported in the first paper (I) appended to the thesis, we identified and analyzed insertion/deletion mutations (INDELs) inferred to have resulted from a sequence repeat-mediated excision mechanism. We found eight new Regions of Difference (RDs) among Francisella strains. Using RDs together with single nucleotide polymorphisms (SNPs), we were able to predict an evolutionary scenario for F. tularensis in which Francisella novicida was the oldest variety while F. tularensis subsp. holarctica was the youngest. We also found that all virulence-attenuated isolates analyzed had deletions at two specific genetic regions - denoted RD18 and RD19 – suggesting that repeat-mediated excision is a mechanism of attenuation in F. tularensis. In subsequent studies (presented in paper II), we developed a combined analysis of INDELs lacking flanking repeats and variable number of tandem repeats (VNTRs). Both markers could be assayed using the same analytical equipment. The inclusion of INDELs provided increased phylogenetic robustness compared with the use of VNTRs alone, while still maintaining a high level of genetic resolution. In analyses described in the next paper (III), we selected INDELs from paper (II) and discovered novel SNPs by DNA comparisons of multiple Francisella strains. Thirty-four phylogenetically informative genetic markers were included in a hierarchical real-time PCR array for rapid and robust characterization of Francisella. We successfully used the assay to genotype 14 F. tularensis isolates from tularemia patients and DNA in six clinical ulcer specimens. Finally, in paper (IV) we demonstrated a strategy to enhance epidemiological investigations of tularemia by combining GIS-mapping of disease-transmission place collected from patient interviews, with high-resolution genotyping of F. tularensis subsp. holarctica isolates recovered from tularemia patients. We found the geographic distributions of specific F. tularensis subsp. holarctica sub-populations to be highly localized during outbreaks (infections by some genotypes being restricted to areas as small as 2 km2), indicative of a landscape epidemiology of tularemia with distinct point sources of infection. In conclusion, the results acquired during the studies underlying this thesis contribute to our understanding of the genetic genealogy of tularemia at both global and local outbreak scales.
28

Neighborhood socioeconomic position and tuberculosis transmission: a retrospective cohort study

Oren, Eyal, Narita, Masahiro, Nolan, Charles, Mayer, Jonathan 27 April 2014 (has links)
UA Open Access Publishing Fund Background: Current understanding of tuberculosis (TB) genotype clustering in the US is based on individual risk factors. This study sought to identify whether area-based socioeconomic status (SES) was associated with genotypic clustering among culture-confirmed TB cases. Methods: A retrospective cohort analysis was performed on data collected on persons with incident TB in King County, Washington, 2004–2008. Multilevel models were used to identify the relationship between area-level SES at the block group level and clustering utilizing a socioeconomic position index (SEP). Results: Of 519 patients with a known genotyping result and block group, 212 (41%) of isolates clustered genotypically. Analyses suggested an association between lower area-based SES and increased recent TB transmission, particularly among US-born populations. Models in which community characteristics were measured at the block group level demonstrated that lower area-based SEP was positively associated with genotypic clustering after controlling for individual covariates. However, the trend in higher clustering odds with lower SEP index quartile diminished when additional block-group covariates. Conclusions: Results stress the need for TB control interventions that take area-based measures into account, with particular focus on poor neighborhoods. Interventions based on area-based characteristics, such as improving case finding strategies, utilizing location-based screening and addressing social inequalities, could reduce recent rates of transmission.
29

Minimally invasive prenatal diagnosis

Overton, Timothy Graeme 2000 (has links)
No description available.
30

Evaluation of insertion-deletion polymorphisms with the kit Qiagen Investigator® DIPplex for forensic application in South Africa

Jacobs, Gwynneth 2015 (has links)
>Magister Scientiae - MSc Insertion-deletion polymorphisms (indels) have been underutilized in forensic identification of individuals in comparison with single nucleotide polymorphisms (SNPs) and short tandem repeat (STRs) systems. The use of indels for the purpose of human identification is more advantageous than previously used methods as it combines desirable characteristics of both the SNPs and STRs i.e. low costs and simplistic typing methods as well as indels having small amplicons size, making them suitable for genotyping highly degraded DNA. Currently there is only one commercial kit available for the forensic community, the Investigator® DIPlex kit (Qiagen), which cover a total of 30 indel loci distributed over 19 autosomal chromosomes. The objective of this study was to evaluate the Qiagen Investigator® DIPplex kit for forensic application in South Africa. The kit‘s performance was evaluated by comparing different extraction methods; sensitivity, robustness and reproducibility were evaluated and forensic parameters (match probability, power of discrimination, polymorphism information content, power of exclusion and typical paternity index) were estimated based on population data generated from five South African populations (Afrikaner, Mixed Ancestry, Indian-Asian, Xhosa and Zulu). Population comparisons were performed using Fst-analysis, factorial component analysis as well as phylogenetic tree construction. DNA was extracted from buccal swabs and whole blood collected from a total of 512 individuals from the five South African population groups and genotyped using the Qiagen Investigator® DIPplex kit. Sanger DNA sequencing and sequence alignments confirmed the presence of a null allele at locus HLD97 which was present in high frequency in the Xhosa and Zulu populations. This observation was made in 14 individuals belonging to the Xhosa and Zulu populations. Null allele frequencies in all five South African populations were also estimated. Null alleles were estimated for all loci using analytical methods i.e. Charkraborty null allele estimator, Brookfield null allele estimators 1 and 2 and ML-NullFreq software program. The kit performed well in the laboratory, not requiring any additional reagents or instrumentation and successfully generating profiles with input DNA amounts as low as 0.2 ng/μL. Although well suited for forensic application, the Qiagen Investigator® DIPplex kit showed some drawbacks with regards to application on South African populations. The presence of a null allele at the HLD97 locus as well as indication of population substructure affects allele frequency estimates for the South African populations. Correction for population substructure as present within the South African populations should be considered using FST analysis and it is recommended that the HLD97 locus should be excluded from any kinship analysis performed on South African populations.

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