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121.
Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion 总被引:1,自引:0,他引:1
Regier JC; Weigmann BM; Leclerc RF; Friedlander TP 《Molecular biology and evolution》1994,11(1):72-87
The silkmoth chorion has provided a stimulating model for the study of
evolution and developmental regulation of gene families. Previous attempts
at inferring relationships among chorion sequences have been based on
pairwise comparisons of overall similarity, a potentially problematic
approach. To remedy this, we identified the alignable regions of low
sequence variability and then analyzed this restricted database by
parsimony and neighbor-joining methods. At the deepest level, the chorion
sequence tree is split into two branches, called "alpha" and "beta." Within
each branch, early- and late-expressing genes each constitute monophyletic
groups, while the situation with middle-expressing genes remains uncertain.
The HcB gene family appears to be the most basal beta-branch group, but
this conclusion is qualified because the effect of gene conversion on
branching order is unknown. Previous studies by Eickbush and colleagues
have strongly suggested that ErA, HcA, and HcB families undergo gene
conversion within a gene family, whereas the ErB family does not. The
occurrence of conversion correlates with a particular tree structure;
namely, branch lengths are much greater at the base of the family than at
higher internodes and terminal branches. These observations raise the
possibility that chorion gene families are defined by gene conversion
events (reticulate evolution) rather than by descent with modification
(synapomorphy).
相似文献
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P. Willey Alison Galloway Lynn Snyder 《American journal of physical anthropology》1997,104(4):513-528
The interpretation of archaeologically-derived skeletal series is dependent on the elements and portions of elements preserved for examination. Bone and bone portion survival is affected by factors, both intrinsic and extrinsic to the elements themselves, that influence deterioration and preservation. Among the intrinsic variables, the density of the element and element portion are particularly important with respect to the degree of preservation. Recently reported bone mineral density values from a contemporary human sample are compared to the survival of prehistoric limb bones of the Crow Creek specimens, a fourteenth-century massacre skeletal series. The contemporary density values are positively correlated with Crow Creek element and element portion survival. Two calculations of bone mineral density, however, are more closely related to preservation than a third. Such density information has implications for assessing minimum number of elements and individuals and documenting taphonomic processes. Am J Phys Anthropol 104:513–528, 1997. © 1997 Wiley-Liss, Inc. 相似文献
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We studied the courtship and copulation ofFlorinda coccinea (Hentz) and described 18 behavioral acts for this species.F. coccinea exhibits many behaviors typical of the Linyphiidae such as web reduction, abdominal vibration, palpal jabbing, stridulation, pseudocopulation, and prolonged copulation. The numbers of palpal insertions during pseudocopulation and copulation are positively correlated to the durations of these phases. Pseudocopulation requires over three times more time on average than copulation, although females copulate longer than is required for fertilization. We found no correlation between the durations of pseudocopulation or copulation and fitness characters, and we hypothesize that lengthy pseudocopulation and copulation may function as a form of internal courtship. 相似文献
127.
Marc BM Bracke Sandra A Edwards Bas Engel Willem G Buist Bo Algers 《Acta veterinaria Scandinavica》2008,50(1):29
Background
Recently, a Risk Assessment methodology was applied to animal welfare issues in a report of the European Food Safety Authority (EFSA) on intensively housed calves. 相似文献128.
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Zoltán Bánki Wilfried Posch Asim Ejaz Verena Oberhauser Suzanne Willey Christoph Gassner Heribert Stoiber Ulf Dittmer Manfred P. Dierich Kim J. Hasenkrug Doris Wilflingseder 《PLoS pathogens》2010,6(4)
Previous studies have demonstrated the involvement of complement (C) in induction of efficient CTL responses against different viral infections, but the exact role of complement in this process has not been determined. We now show that C opsonization of retroviral particles enhances the ability of dendritic cells (DCs) to induce CTL responses both in vitro and in vivo. DCs exposed to C-opsonized HIV in vitro were able to stimulate CTLs to elicit antiviral activity significantly better than non-opsonized HIV. Furthermore, experiments using the Friend virus (FV) mouse model illustrated that the enhancing role of complement on DC-mediated CTL induction also occurred in vivo. Our results indicate that complement serves as natural adjuvant for DC-induced expansion and differentiation of specific CTLs against retroviruses. 相似文献