Browsing by Subject "Recombinant DNA"
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Item Distribution and organization of repetitive DNA sequences on human chromosome-16(Texas Tech University, 1993-12) Longmire, Jonathan L.This study Is comprised of two distinct but related parts. Chapter II reports on the development of partial digest bacteriophage and cosmid libraries made from flow sorted human chromosome-16. These chromosome-specific libraries are powerful new tools for physical and genetic mapping of the human genome and make It possible to examine the organization of repetitive DNA sequences on specific human chromosomes. Chapter III presents a comprehensive investigation into the representation of many repetitive DNA sequence families In the human chromosome 16-specific cosmid library. Data obtained In this study were compared to previously described values for the abundance of the same repetitive elements in total human nuclear DNA. In addition, certain highly polymorphic repetitive sequences were localized onto the emerging physical map of chromosome-16. This study Is the first comprehensive examination of repeated sequences on a single human chromosome and provides a foundation for the future integration of the physical and genetic maps of human chromosome-16. Chapter IV contains a synthesis of the study. In addition, a critical assessment Is made of new technologies that were used In this study and that are becoming increasingly Important to other genome-related studies. Problems that were incountered through the course of this study are Identified and possible solutions are discussed. Finally, future lines of investigation for continuation and expansion of these studies Into the biology of repetitive DNA sequences are discussed.Item Expression and function of the JunD transcription Factors: JunD-FL and Delta-JunD(Texas Tech University, 2003-08) Short, John DJunD is a member of the Jun family of basic region leucine zipper proteins that can form homodimers or form heterodimers with other Jun family members (c-Jun and JunB) or Fos family members (c-Fos, FosB, Fra-1, Fra-2). Collectively, these dimer combinations make up the Activator Protein-1 (AP-1) transcription factor. AP-1 binds to the TPA-response element, TGAG/CTCA, within the promoter of a wide-range of genes, many of which are important for cell growth regulation. JunD functions as a negative regulator of transformed cell growth and antagonizes transformation by the ras oncogene. JunD also functions to protect cells from premature senescence and apoptosis. The junD gene, like the other jun genes, is intronless and generates a single mRNA. However, we have found that the JunD mRNA generates two predominant JunD protein isoforms through alternative translational initiation. The larger JunD isoform, JunD-FL (39 kD) is generated by translational initiation at the first AUG downstream of the m7-G cap, and the smaller JunD isoform, AJunD (34 kD), is generated by translational initiation at the third AUG codon from the m7-G cap. These AUG codons are in-frame, making JunD-FL a 48-amino acid N-terminal extension of ÄJunD. We have also identified four other potential translational initiation events that occur at both AUG and non-AUG start codons within the JunD mRNA, suggesting that there are six peptides generated from the JunD mRNA. JunD-FL and AJunD function differentially within the cell. Both JunD isoforms bind to Jun-N-terminal kinases (JNKs), but JNKs more potently stimulate transactivation of JunD-FL in vitro. In addition, JunD-FL interacts with the Menin tumor suppressor protein. Menin inhibits transcriptional activity of JunD-FL in vitro, but does not bind to or inhibit ÄJunD transcriptional activity. We have identified several putative target genes of JunD-FL and ÄJunD, including the nuclear orphan receptor nur77, which is involved in cell growth arrest and cellular apoptosis. We found that Nur77 is positively regulated by JunD-FL and ÄJunD in a similar manner but is negatively regulated by c-Jun.Item Genetic variation of heat tolerance and correlation with other agronomic traits in a maize (Zea mays L.) recombinant inbred line population(Texas Tech University, 2003-08) Bai, JiangpingHeat stress is a critical environmental factor that affects agricultural production in the southwest of the United States, especially in West Texas. Heat stress can reduce plant height, kill the leaf tissues, cause abortion of pollen and kernel, and affect the cell activities. The objectives of this study were to determine the genetic variation of leaf firing, chlorophyll fluorescence, plant height, ear height, leaves above ear, number of tassel branches, days to flowering and yield per plant in a recombinant inbred line population, and to estimate the heritability of those traits. A total of 179 maize recombinant inbred lines from B76 x B106 were evaluated at Pecos, TX, in 2001, at Texas Tech University (TTU) experimental farm in 2002, and at TAMU Lubbock center in 2001 and 2002. Significant variation in leaf firing, chlorophyll fluorescence and other agronomic traits were found among the RILs. In the population, leaf firing ranged from 0% to 92.9% in Lubbock-TAMU 2001 test, 0% to 100% in Pecos 2001 test, 0% to 67.9% in Lubbock-TAMU 2002 test, and 0% to 100% in Lubbock-TTU 2002 test. The average of chlorophyll fluorescence of the RILs ranged from 0 to 0.79 (2001 Lubbock-TAMU), 0.14 to 0.78 (2002 Lubbock-TAMU), and 0.02 to 0.76 (2002 Lubbock-TTU). Leaf finng,chlorophyll fluorescence and other agronomic traits also showed transgressive segregation in the population in each environment. Only plant height, ear height, number of tassel branches (2001 and 2002 Lubbock-TAMU), and leaves above ear (2002 Lubbock-TAMU) showed the normality distribution. Under heat stress, yield per plant was negatively correlated with percent leaf finng and days to flowering and positively correlated with chlorophyll fluorescence and number of tassel branches. Percent leaf firing was negatively correlated vMth chlorophyll fluorescence. Number of tassel branches was positively correlated with plant height and ear height. Leaf firing and chlorophyll fluorescence did not show strong correlation with plant height, ear height, number of tasel branches, and leaves above ear. The broad-sense heritability for leaf firing and chlorophyll fluorescence was 0.32 and 0.28 on the plot basis, respectively, and 0.85 and 0.77 on the mean basis. From their low heritability based on plot, high heritability based on means, and large genotype x environment interactions, we believe that the heat tolerance in maize is inherited quantitatively, and effective selection for heat tolerance requires evaluation genotypes in replicated trails in multiple environments.Item Overexpression of higher plant nitrite reductase(Texas Tech University, 1999-05) Li, XinThe gene encoding the ferredoxin-dependent nitrite reductase of spinach chloroplasts (NiR; EC 1.7.7.1) has been isolated and sequenced (Back et ah, 1988). Although some information is available about the possible role of a few specific amino acids in the enzyme mechanism (Hirasawa et ah, 1994; Bellissimo et fl/.,1995; Dose et ah, 1997 and Dose, 1996), the absence of a 3-dimensional structure for the protein and the scarcity of data obtained with site-specific mutants have left considerable uncertainty about the enzyme mechanism. The work presented in this dissertation represents an attempt to address, in part, these issues by designing a system to over-express NiR in Escherichia coli and investigate the roles of the tryptophan residue at position 92 in the enzyme mechanism.Item The covalent structure of four salmonellar flagellar filament proteins(Texas Tech University, 1986-05) Wei, Li-naNot available