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Results for “quantitative genetics”

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At least 325 records · Page 18Linked to original sources
PubMed1991

Estimates of quantitative genetic parameters of immunological traits in the chicken.

Three in vivo assays were used to measure the immunocompetence of chickens in two generations of a selection experiment. The obtained data were used to estimate the variance components for sire and dam for antibody production to Pasteurella multocida and Mycoplasma gallisepticum vaccines, for T-cell-mediated immunity evaluated by a phytohemagglutinin wing web assay, and for clearance of foreign particles from the circulatory system. Heritabilities of and genetic correlations among these immunological traits were calculated from the sire variance components. Heritability estimates of the immunological traits based on the sire component of variance ranged from .06 to .53, and genetic correlations among immunological traits were generally negative.

Analysis of Variance↗
PubMed2000

Quantitative genetic variation in CD19 expression correlates with autoimmunity.

Signaling thresholds influence the balance between humoral immunity and autoimmunity. Cell surface CD19 regulates intrinsic and Ag receptor-induced B lymphocyte signaling thresholds, and transgenic mice that overexpress CD19 by 3-fold generate spontaneous autoantibodies in a genetic background not associated with autoimmunity. To quantify the extent that genetically determined differences in expression of a single cell surface molecule can influence autoantibody production, we have assessed autoimmunity in a C57BL/6-transgenic mouse line with subtle 15-29% increases in CD19 cell surface expression (CD19 transgenic). Antinuclear Abs, especially anti-spindle pole Abs, rheumatoid factor, and autoantibodies for ssDNA, dsDNA, and histone were produced in these transgenic mice, but not littermate controls. This demonstrates that small changes in CD19 expression can induce autoantibody production. Remarkably, similar changes in CD19 expression were found on B cells from patients with systemic sclerosis, a multisystem disorder of connective tissue with autoantibody production. CD19 density on blood B cells from systemic sclerosis patients was significantly ( approximately 20%) higher compared with normal individuals, whereas CD20, CD22, and CD40 expression were normal. These results suggest that modest changes in the expression or function of regulatory molecules such as CD19 may shift the balance between tolerance and immunity to autoimmunity. Thereby autoimmune disease may result from a collection of subtle multigenic alterations that could include incremental density changes in cell surface signaling molecules.

Adult↗
PubMed2000

Racial differences in birth health risk: a quantitative genetic approach.

In the United States the gap between black and white babies' birth weights has remained largely unexplained. Rather than trying to measure all relevant variables, we used a genetically informative design to study the relative importance of genetic and environmental factors. Employing multiple indicators of "birth health risk," we found that the racial differences increased with the magnitude of the shared environmental effects. This suggested that possible genetic effects would not pertain to fetal genes, although genes affecting the mother's physical or physiological characteristics could be important because they contribute to shared environment in our analysis.

Adolescent↗
PubMed2002

[Quantitative genetic analysis and multiple trait selection of pharmaceutical composition on Ginkgo biloba L. leaves].

The China possesses more than 70% Ginkgo resources in the world. The purposes of this research are to collect fine seedling and grafting clones in China, to probe genetic law on flavone glycosides and terpenes on Ginkgo leaves, and select leaf-used cultivars of high-pharmaceutical composition. In this research, we have collected 87 clones from 13 provenances and have carried out randomized block experiment at Tancheng, Laizhou and Yaoxiang in Shandong Province. Flavone glycosides and terpenes were determined through HPLC method from an improved Van Beek (1991) techniques and Shimadzu Lc-10 AD (Japan). Data and breeding analyses were carried out through IBMPC and SPQG30 software. The results of variance analyses show that there are significant differences to flavone glycosides, terpenes in clones, and the law of genetic parameters on heritability (h2) and genetic variability coefficient (Gcv), is clone > sex > provenance to flavone glycosides in ginkgo leaves. The sigma g2, h2, Gcv and delta G' in male tree clone leaves are higher than female clone leaves on flavone glycosides. We have found that there is a maximum flavone content clone among males and a maximum terpene clone among females. The results of Q-cluster analyses are consistent with R-factor analyses of twenty higher terpenes clones. The results of index selection show that the ri.Y2, E(I) and CGS' of multiple traits selection including (gamma) trait are higher than single trait and multiple traits selection excluding gamma. The direct or index selection is more suited to leaf-used cultivars of Ginkgo. The genetic stability of each clone was appraised by Wricke's ecovalence method and Nassar & Huhu noparameter method. Flavone glycosides and terpenes are more than 2.09%-2.57% and 0.33%-0.41%, respectively, and we have selected four clones.

Breeding↗