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D. T. Morgan Jr. 《Genetica》1976,46(2):133-138
Monoploids in Zea mays L. occur spontaneously among individual diploid seedlings. Plants with the gametic chromosome number have also been detected among members of multiple seedlings of maize and numerous other species of angiosperms. Previous reports disclosed that Xirradiation of the pollen successfully stimulated reduced parthenogenesis in some other angiosperms, but the results of X-ray treatment were inconclusive in maize. Therefore, a tester stock of maize homozygous for lg
land gl
l was crossed with pollen from inbred CI3A, carrying the dominant alleles. The pollen was exposed to 0, 1000, 2000, and 4000r units of X rays. chromosome counts were made from root tips of plants exhibiting both recessive phenotypes to establish the frequencies of monoploids in the control and X1 populations.Monoploids were more abundant among the individual seedlings from crosses with untreated pollen than in the X1 populations. X irradiation of the pollen is not a feasible method for the induction of monoploids in maize. The X-ray treatments greatly increased the frequency of multiple seedlings, and deficiencies were numerous among them. The members of a set of multiple seedlings were always genetically identical, and no monoploid members occurred. It is concluded that the induced deficiencies caused atypical development resulting in zygotic or embryonic cleavage.Scientific Article No. A2070, Contribution No. 5023 of the Maryland Agricultural Experiment Station, Department of Botany. 相似文献
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The nature of the human blood group P1 determinant 总被引:4,自引:0,他引:4
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Detergent soluble extracts of differentiated regions of the Porphyra perforata J. Ag. thallus (holdfast, rhizoidal, vegetative and reproductive cells) were fractionated on sodium dodecyl sulfate polyacrylamide gels. Glycoproteins were identified by their lectin affinity. Extracts from all areas of the thallus contained glycoproteins, but the staining patterns were different for each region with each of the lectins tested: concanavalin A, Ulex europeaus agglutinin, Ricinus communis agglutinin, soybean agglutinin and peanut agglutinin. These data indicate that the morphologically distinct regions of the thallus also differ biochemically. Analysis of the lectin blots revealed the presence of tissue-specific glycoproteins in the five thallus areas. Such unique glycoproteins could be used as markers of differentiation in this species. 相似文献
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Abalone are semimobile marine gastropods that form the basis of Australia's second most valuable fishery. A site off the coast of Port Arthur, Tasmania, was visited on six occasions. On each occasion, any unmarked live abalone found were marked with a unique identification number and were recorded. Any previously marked abalone found had its identification number and whether or not it was still alive recorded. This results in integrated mark-recapture-recovery data, as in Catchpole et al. (1998, Biometrics 54, 33-46). During the study period, abalone grew in size, and we model the survival of individuals as a function of their size, estimated from a fitted growth curve. The shells of dead animals are long lasting, and we extend existing methodology to allow for the possibility that an animal found dead may have been dead but overlooked for several visits. 相似文献
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Earlier studies have shown that transferrin binds to specific receptors on the reticulocyte surface, clusters in coated pits and is then internalized via endocytic vesicles. Guinea-pig reticulocytes also have specific receptors for ferritin. In this paper ferritin and transferrin endocytosis by guinea-pig reticulocytes was studied by electron microscopy using the natural electron density of ferritin and colloidal gold-transferrin (AuTf). At 4 degrees C both ligands bound to the cell surface. At 37 degrees C progressive uptake occurred by endocytosis. AuTf and ferritin clustered in the same coated pits and small intracellular vesicles. After 60 min incubations the ligands colocalized to large multivesicular endosomes (MVE), still membrane-bound. MVE subsequently fused with the plasma membrane and released AuTf, ferritin and inclusions by exocytosis. All endocytic structures labelled with AuTf contained ferritin, but 23 to 35% of ferritin-labelled endocytic structures contained no AuTf. These data suggest that ferritin and transferrin are internalized through the same pathway involving receptors, coated pits and vesicles, but that these proteins are recycled only partly in common. 相似文献