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141.
Chiu Wan-Ling Johnson Ellen M. Kaplan Sara A. Blasko Kimberly Sokalski Mary B. Wolfson Ruth Sears Barbara B. 《Molecular genetics and genomics : MGG》1990,221(1):59-64
Molecular Genetics and Genomics - Oenothera plants homozygous for a recessive allele at the plastome mutator (pm) locus show non-Mendelian mutation frequencies that are 1000-fold higher than... 相似文献
142.
Microsatellite genetic distances between oceanic populations of the humpback whale (Megaptera novaeangliae) 总被引:1,自引:0,他引:1
Valsecchi E; Palsboll P; Hale P; Glockner-Ferrari D; Ferrari M; Clapham P; Larsen F; Mattila D; Sears R; Sigurjonsson J; Brown M; Corkeron P; Amos B 《Molecular biology and evolution》1997,14(4):355-362
Mitochondrial DNA haplotypes of humpback whales show strong segregation
between oceanic populations and between feeding grounds within oceans, but
this highly structured pattern does not exclude the possibility of
extensive nuclear gene flow. Here we present allele frequency data for four
microsatellite loci typed across samples from four major oceanic regions:
the North Atlantic (two mitochondrially distinct populations), the North
Pacific, and two widely separated Antarctic regions, East Australia and the
Antarctic Peninsula. Allelic diversity is a little greater in the two
Antarctic samples, probably indicating historically greater population
sizes. Population subdivision was examined using a wide range of measures,
including Fst, various alternative forms of Slatkin's Rst, Goldstein and
colleagues' delta mu, and a Monte Carlo approximation to Fisher's exact
test. The exact test revealed significant heterogeneity in all but one of
the pairwise comparisons between geographically adjacent populations,
including the comparison between the two North Atlantic populations,
suggesting that gene flow between oceans is minimal and that dispersal
patterns may sometimes be restricted even in the absence of obvious
barriers, such as land masses, warm water belts, and antitropical migration
behavior. The only comparison where heterogeneity was not detected was the
one between the two Antarctic population samples. It is unclear whether
failure to find a difference here reflects gene flow between the regions or
merely lack of statistical power arising from the small size of the
Antarctic Peninsula sample. Our comparison between measures of population
subdivision revealed major discrepancies between methods, with little
agreement about which populations were most and least separated. We suggest
that unbiased Rst (URst, see Goodman 1995) is currently the most reliable
statistic, probably because, unlike the other methods, it allows for
unequal sample sizes. However, in view of the fact that these alternative
measures often contradict one another, we urge caution in the use of
microsatellite data to quantify genetic distance.
相似文献
143.
Merla Hubler Lee A. Niswander James Peters Karen E. Sears 《Journal of morphology》2010,271(7):769-776
During their embryogenesis, marsupials develop a unique structure, the shoulder arch, which provides the structural and muscle‐attachment support necessary for the newborn's crawl to the teat. One of the most pronounced and important aspects of the shoulder arch is an enlarged coracoid. After marsupial newborns reach the teat, the shoulder arch is remodeled and the coracoid is reduced to a small process on the scapula. Although an understanding of marsupial coracoid reduction has the potential to provide insights into both, marsupial evolution and the origin of mammals, little is known about the morphological and cellular processes controlling this process. To remedy this situation, this study examined the morphological and cellular mechanisms behind coracoid reduction in the gray short‐tailed opossum, Monodelphis domestica. A quantitative, morphometric study of shoulder girdle development revealed that the coracoid is reduced in size relative to other aspects of the shoulder girdle by growing at a slower rate. Using a series of molecular assays for cell death, no evidence was found for programmed cell death playing a role in the reduction of coracoid size in marsupials (in contrast to hypotheses of previous researchers). Although it is likely the case that coracoid growth is reduced through a relatively lower rate of cellular proliferation, differences in proliferative rates in the coracoid and scapula were not great enough to be quantified using standard molecular assays. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc. 相似文献
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149.
Urban physiology: city ants possess high heat tolerance 总被引:1,自引:0,他引:1
Urbanization has caused regional increases in temperature that exceed those measured on a global scale, leading to urban heat islands as much as 12 degrees C hotter than their surroundings. Optimality models predict ectotherms in urban areas should tolerate heat better and cold worse than ectotherms in rural areas. We tested these predications by measuring heat and cold tolerances of leaf-cutter ants from South America's largest city (S?o Paulo, Brazil). Specifically, we compared thermal tolerances of ants from inside and outside of the city. Knock-down resistance and chill-coma recovery were used as indicators of heat and cold tolerances, respectively. Ants from within the city took 20% longer to lose mobility at 42 degrees C than ants from outside the city. Interestingly, greater heat tolerance came at no obvious expense of cold tolerance; hence, our observations only partially support current theory. Our results indicate that thermal tolerances of some organisms can respond to rapid changes in climate. Predictive models should account for acclimatory and evolutionary responses during climate change. 相似文献
150.
D Robin Taylor Piush Mandhane Justina M Greene Robert J Hancox Sue Filsell Christene R McLachlan Avis J Williamson Jan O Cowan Andrew D Smith Malcolm R Sears 《Respiratory research》2007,8(1):82-9