Browsing by Subject "Major Histocompatibility Complex"
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Item Analysis of Haplotype Structure in the Bovine Major Histocompatibility Complex(2011-02-22) Fritz, Krista L.The goal of this project was to identify and characterize polymorphic markers spanning regions of the bovine major histocompatibility complex (BoLA) to analyze patterns of genetic variation and haplotype structure across diverse cattle breeds with various breed histories and selection pressures. Genetic markers that demonstrated sufficient levels of polymorphism, locus specificity, Mendelian inheritance, and the accurate typing of alleles across diverse haplotypes were chosen to define separate haplotype structures for the BoLA IIb and BoLA IIa-III-I regions and to evaluate breakpoints in linkage disequilibrium within the regions surrounding BoLA IIa-III-I. A total of 23 microsatellites, two SNPSTRs, 62 SNPs, and the alleles of three class IIa genes were selected for use in this study. These markers revealed eleven recombination events, low levels of recombination in BoLA IIa-III-I, a sharp break in haplotype structure in the region centromeric to class IIa, prolonged linkage disequilibrium in the extended class I region, strong conservation of BoLA IIa-III-I haplotype structure, BoLA IIa-III-I homozygous haplotype identity across seven different breeds of cattle, and a small number of common BoLA IIa-III-I haplotypes within the Angus and Holstein breeds. This work demonstrated that 52 SNPs from the Illumina 50K SNPchip could accurately predict BoLA IIa-III-I haplotypes. These 52 SNPs represent tagSNPs that can predict BoLA IIa-III-I genetic variation and could offer a cost-effective means for screening large sample sizes for haplotype/disease association studies in the future.Item Sequence assembly and annotation of the bovine major histocompatibility complex (BoLA) class IIb region, and in silico detection of sequence polymorphisms in BoLA IIb(Texas A&M University, 2007-04-25) Childers, Christopher P.Cattle are vitally important to American agriculture industry, generating over 24.6 billion pounds of beef (by carcass weight), and 79.5 billion dollars in 2005, and over 27 billion dollars in milk sales in 2004. As of July 2006, the U.S. beef and dairy industry is comprised of 104.5 million head of cattle, 32.4 million of which were processed in 2005. The health of the animals has always been an important concern for breeders, as healthy animals grow faster and are more likely to reach market weight. Animals that exhibit natural resistance to disease do not require chemicals to stimulate normal weight gain, and are less prone to disease related wasting. The major histocompatibility complex (MHC) is a collection of genes, many of which function in antigen processing and presentation. The bovine MHC (BoLA) differs from typical mammalian MHCs in that the class II region was disrupted by a chromosomal inversion into two subregions, designated BoLA IIa and BoLA IIb. BoLA IIb was transposed to a position near the centromere on bovine chromosome 23,while BoLA IIa retains its position in BoLA. Comparative sequence analysis of BoLA IIb with the human MHC revealed the location of the region containing the proximal inversion breakpoint. Gene content, order and orientation of BoLA IIb are consistent with the single inversion hypothesis when compared to the corresponding region of the human class II MHC (HLA class II). BoLA IIb spans approximately 450 kb. The genomic sequence of BoLA IIb was used to detect sequence variation through comparison to other bovine sequences, including data from the bovine genome project, and two regions in the BAC scaffold used to develop the BoLA IIb sequence. Analysis of the bovine genome project sequence revealed a total of 10,408 mismatching bases, 30 out of 231 polymorphic microsatellites, and 15 sequences corresponding to the validated SNP panel generated by the bovine genome sequencing project. The two overlapping regions in the BoLA IIb BAC scaffold were found to have 888 polymorphisms, including a total of 6 out of 42 polymorphic microsatellites indicating that each BAC derived from a different chromosome.