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Goats and some sheep synthesize a juvenile hemoglobin, Hb C (alpha 2 beta
C2), at birth and produce this hemoglobin exclusively during severe anemia.
Sheep that synthesize this juvenile hemoglobin are of the A haplotype.
Other sheep, belonging to a separate group, the B haplotype, do not
synthesize hemoglobin C and during anemia continue to produce their adult
hemoglobin. To understand the basis for this difference we have determined
the structural organization of the beta- globin locus of B-type sheep by
constructing and isolating overlapping genomic clones. These clones have
allowed us to establish the linkage map 5' epsilon I-epsilon II-psi beta
I-beta B-epsilon III-epsilon IV- psi beta II-beta F3' in this haplotype.
Thus, B sheep lack four genes, including the BC gene, and have only eight
genes, compared with the 12 found in the goat globin locus. The goat
beta-globin locus is as follows: 5' epsilon I-epsilon II-psi beta X-beta
C-epsilon III-epsilon IV-psi beta Z-beta A-epsilon V-epsilon VI-psi beta
Y-beta F3'. Southern blot analysis of A-type sheep reveals that these
animals have a beta- globin locus similar to that of goat, i.e., 12 globin
genes. Thus, the beta-globin locus of B-haplotype sheep resembles that of
cows and may have retained the duplicated locus of the ancestor of cows and
sheep. Alternatively, the B-sheep locus arrangement may be the result of a
deletion of a four-gene set from the triplicated locus.
相似文献
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Spinach ferredoxin contains a single ferredoxin which can be chemically modified with diethylpyrocarbonate. By varying the concentration of diethylpyrocarbonate modified ferredoxins could be prepared which had only one or both of the imidazole nitrogens of the histidine modified. A small amount of tyrosine was also modified. Ferredoxin with only one of the imidazole nitrogens modified was fully active in NADP photoreduction by chloroplast membranes. This activity was lost as the second imidazole nitrogen was modified. The results suggest an essential role for the single histidine of ferredoxin. 相似文献
5.
In cotton plants ( Gossypium hirsutum L. cv. B.J.A.) the temperature of the roots affected both root and shoot growth, as did the temperature of the shoot. Drought resistance increased when the temperature imposed on roots (27°C) was lower than that imposed on shoots (17°C); the result was a decrease in both transpiration and flow of root sap. Stomatal characteristics as measured by density, index and resistance, depended only on shoot temperature. Differences in drought resistance, depended only on shoot temperature. Differences in drought resistance seem to be a result of changes in transpiration flow modulated by the amount of absorbed water. 相似文献
6.
Eggs of the tambaqui Colossoma macropomum were incubated at 28 and 31) C. Somitogenesis started shortly after the formation of the neural plate and notochord. New somites were added at the rate of one every 13 min at 28) C and one every 11 min at 31) C. Myogenesis started in the most rostral myotomes at the 9-somite stage and proceeded in a caudal direction. Mononuclear myotubes with the morphological characteristic of muscle pioneer cells were observed lateral to the notochord. The majority of myotubes were formed from the fusion of 3–6 spindle-shaped myoblasts. Myofibril synthesis started soon after cell fusion at the periphery of myotubes. Close membrane contacts and 'gap'-type junctions were observed between myotubes, immature muscle fibres and at the inter-somite boundary, suggesting that the cells were electrically coupled. Embryos exhibited rhythmic movements at the 20-somite stage, and hatched at the 29–30-somite stage 15–18 h post-fertilisation (PFT) at 28° C and 11 h PFT at 31° C. Larvae hatched at a comparatively early stage of development prior to the completion of somitogenesis and the formation of eye pigment, pectoral fins and jaws. The myotomes comprised a single superficial layer of well-differentiated muscle fibres which contained abundant mitochondria, overlying an inner core of myotubes (presumptive white muscle layer). Differentiation and growth during the larval stages was extremely rapid, and the juvenile stage was reached after little more than 6 days at 28° C. 相似文献
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Seed of Stlosanthes humilis both have hard integuments and display physiological dormancy, the latter being lost during post-harvest ageing. Ethrel and l-aminocyclopropane-1-carboxylic acid (ACC) partially released scarified young seed from physiological dormancy. Cobalt and silver ions and abscisic acid inhibited germination of scarified non-dormant seed. Abscisic acid also inhibited germination of voung seed promoted by ACC. Thiourea and ethrel plus benzyladenine showed the greatest efficacy in breaking seed dormancy. 相似文献
10.
Bertrand D. Eardly Mara Cloutier Taejung Chung Sofia Roitman Fabricio R. Vieira Mary Ann V. Bruns 《Restoration Ecology》2023,31(1):e13695
From 1913 to 1980, two zinc smelters in Palmerton, Pennsylvania, emitted large quantities of atmospheric pollutants nearly eliminating forests along a ridge above the town. In 2008, a remediation treatment was applied to the land above one of the smelters that included the planting of several locally adapted plant species. It also included mineral fertilization and mycorrhizal inoculation. One of the species, the Pitch pine (Pinus rigida, Mill.), is a native tree that is both tolerant of metalliferous soils and obligatorily ectomycorrhizal. This report summarizes the results of two observational studies conducted 5 years after the remediation treatment. The first study's objective was to compare ectomycorrhizal communities on treated Pitch pine saplings, with communities on naturally regenerating saplings in an adjacent non-remediated area. The second study's objective was to determine if the composition of the fungal communities on root tips of naturally regenerating Pitch pine saplings differed with distance from the smelters. Fungal community compositions were determined using internal transcribed spacer rRNA sequences. Comparisons of sequences from the remediated and non-remediated sites revealed that communities at the remediated sites had lower taxonomic diversity and were dominated by members of a genus in the remediation inoculant. The results of the smelter-proximity study indicated that although fungal diversity did not differ markedly with distance from the smelters, the relative abundances of some taxa were greater on saplings growing directly above the smelters, where the soils contained highest concentrations of zinc and cadmium. 相似文献