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1.
雀形目八种鸟核型的比较研究A   总被引:4,自引:0,他引:4  
本文分析了雀形目8种鸟的核型,并与已报道的资料进行了比较。结果表明, 近缘种间及属间核型差异不大,从而支持了鸟类核型在进化过程中有较强保守性这一观点。 Abstract:The karyotypes of 8 species of Passerine birds were studied and compared with the data reported before.The result showed that the difference of karyotypes between relative species of genera is not obvious,thus providing the hypothesis that bird karyotype is exceedingly conservative in the course of evolution.  相似文献   

2.
The meiotic behavior of 10 taxa (nine species and one variety) of the genus Pinus was investigated using pollen mother cells (PMCs) to reveal the differentiation among karyotypes. Chromosome spreads were prepared by conventional squashing. The meiotic index and the average configuration were higher, whereas the frequency of aberrance (chromosomal bridges, fragments, or micronuclei) was lower, in all 10 taxa compared with other gynmosperms. The meiotic index, average configuration, and frequency of irregularity were found to be uniform among the species. It was shown that the genomes of the Pinus species investigated were highly stable, confirming results of previous mitotic analyses in this genus. However, slight differentiation of homologous chromosomes among genomes was revealed by analysis of meiotic configurations in Pinus nigra var. poiretiana. Quadrivalents were observed in 9.31% of PMCs in this species. This is the first time that quadrivalents have been observed in gymnosperms.  相似文献   

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In the present study, the karyotypes of 34 populations belonging to 11 species and one variety of Heracleum from the Hengduan Mountains in China were examined. Chromosome numbers and the karyotypes of three species (H. souliei, H. la'ngdoni, and H. wenchuanense) are reported for the first time, as are the karyotypes of H. moellendorffii and H. henryi (tetraploid). Populations of H. candicans, H. franchetii, and H. kingdoni in the Hengduan Mountains were found to consist of a mixture of diploid and tetraploid plants. Except for four species of Heracleum, namely H. candicans, H. franchetii, H. henryi, and H.kingdoni, which have both diploid and tetraploid karyotypes, all other species of Heracleum are were found to be diploid. All karyotypes were found to belong to the 2A type of Stebbins, with the exception ofH. candicans var. obtusifolium, which belongs to 2B, and H. hemsleyanum and H. franchetii (Mt. Dujuan, Daocheng, Sichuan, China), which belong to 1A. There was only a slight difference in the karyotype asymmetry index, which suggests a close kinship for species of Heracleum and that the entire phylogenetic development of Heracleum is relatively primitive. Species that exhibited advanced morphological features were also more advanced in karyotype structure, with the order ofkaryotype evolution being 1A→2A→2B. This phenomenon indicates that the species distributed in the Hengduan Mountains have not diverged completely and that the Hengduan Mountains are a relatively young and active area for the evolution of Heracleum. Polyploidization in Heracleum may be an important evolutionary mechanisms for some species, generating diversity. The biological attributes, distribution range, and the geological history of the genus have all played a part in accelerating the evolution through polyploidization or aneuploidization. It is known that as the distribution latitude of Heracleum decreases from north to south, the chromosome number, ploidy level, and asymmetry structure appear to increase. In the Hengd  相似文献   

4.
泽蛙、日本林蛙、饰纹姬蛙不同地理居群的核型多样性   总被引:5,自引:0,他引:5  
钱晓薇  朱睦元 《遗传》2000,22(3):144-148
本文研究了温州地区的泽蛙、日本林蛙、饰纹姬蛙的核型,并分析了9个地理居群泽蛙的核型、4个地理居群日本林蛙的核型和3个地理居群饰纹姬蛙的核型。结果表明,不同地理居群的同种蛙均有相同的染色体数和核型模式。泽蛙、日本林蛙都为 2n=26,NF=52,核模式5+8;饰纹姬蛙 2n=24,NF=48,核模式6+6。但同一种蛙的不同地理居群之间在SM数目和顺序、次缢痕或随体的位置等都有所不同,说明不同地理居群的同种蛙的染色体具有丰富的多样性。故保护蛙品种资源多样性,不仅要从整个群体上考虑,而且要针对每个品种(或类群)进行保护。 Abstract:The karyotypes of Rana limmocharis boie,Rana j.Japonica,and Microhyla ornata from Wenzhou were studied.The karyotypes of nine populations of Rana limmocharis boie,four populations of Rana j.Japonica and three populations of Microhyla ornata from different geographical regions were compared.The results demonstrated that the same species of different geographical populations have the same amount of chromosome and karyotypic formulae. Rana limmocharis boie and Rana j.Japonica have 2n=26,NF=52 and 5+8 karyotypic formulae.Microhyla ornata has 2n=24,NF=48 and 6+6 karyotypic formulae.But some dissimilarities were found among them.First,the number and sequence of submetacentric chromosome were different among them,and then the secondary contriction (SC)or satellite (Sat)were also different.It was showed that the chromosomes of same species of different geographical population have diversities.Conservation of frog genetic diversity must be considered of not only the genetic diversity conservation of the total frog population but also that of every frog breed.  相似文献   

5.
Scanning electron microscopy (SEM) and histological techniques were used to observe and study the setae structures of two gecko species (G. gecko and G. swinhonis) and the relationships between these structures and the adhesive forces. The SEM results showed that the setae of these two species were densely distributed in an orderly fashion, and branched with curved tips. The setae of G. gecko had cluster structures, each cluster containing 4-6 setae whose terminal branches curved towards the center of the toes at ~ 10o, the tips of the branches like spatulae and densely arrayed at an interval of less than 0.2―0.3 μm. On the contrary, the branch tips in the setae of G. swinhonis were curled, and the terminal parts of setae curved towards the center of the toes at various angles. Usually the setae of these gecko species branch twice at the top at intervals greater than that of G. gecko. The histological observation found that inside the setae of these two species there were plenty of unevenly distributed contents, such as epithelia, fat cells, pigmental cells and muscle tissue, but no gland cells existed. The results of functional experiments suggested that modifying the structure of gecko's setae could reduce its adhesive ability dramatically, demonstrating the positive correlation between the structure of the gecko's setae and its adhesive ability. The above results provide important information in designing bio-mimic setae and bio-gecko robots.  相似文献   

6.
The esterase (EST) and the malate dehydrogenase Ⅱ (MDHⅡ) isozymes in A. mellifera carpatica (C), A. mellifera ssp.(D), “Zhejiang Agricultural University No.1” A. mellifera ligustica (Ea) and A. mellifera carnica (K), and the genotypes of MDHⅡ isozymes in four subspecies of A. mellifera were analysed by IEF PAGE. The results indicate that the four subspecies of A. mellifera showed the same EST zymogram, while A. cerana showed a different EST zymogram, which suggests that the genotypes of EST isozymes in A. mellifera are different from those in A. cerana. The genotypes of the MDHⅡ isozymes in four subspecies of A. mellifera were aa, ab, ac, bb, bc and cc. The C and Ea subspecies exhibited high homozyosity, while D and K displayed high heterozyosity. The allele b appeared to be the highest frequency in C, while the allele c had the highest frequency in Ea. The frequencies of the alleles a, b and c in sub species D were very similar. The alleles a and c were common, while allele b was rare in sub species K. There were highly significant differences in genotype frequencies, allele frequencies, homozyosity and heterozyosity among these four subspecies.  相似文献   

7.
Cytological characters of four species in Syncalathium (Asteraceae: Lactuceae), a small genus with six identified species endemic to alpine scree of the Sino-Himalayan region, are surveyed in this report. Three species (Syncalathiumpilosum, Syncalathium chrysocephalum, and Syncalathium disciforme) are examined for the first time. Combined with our previous counts, five species have been cytologically investigated from the genus and the results indicated that all species are diploid with the basic somatic chromosome number of x=8. The karyotype asymmetry of Syncalathium souliei is 2A, distinct from the other four species of 1A, and the remaining species are divided into two subgroups with different karyotypes, consistent with their morphological features. The significance of the cytological evolution of Syncalathium is briefly discussed.  相似文献   

8.
万木林自然保护区不同群落优势种高度结构研究   总被引:3,自引:1,他引:2  
Based on the data of four subtropical evergreen broadleaved forest communities in Wanmulin Natural Reserve, whose dominant species were Tsoongiodendron odorum Chun, Cinnamomum micranthum Hayata, Castanopsis fabri Hance and Pinus massoniana, respectively, the height class and diameter class structures and the dynamics of height structure were analyzed. The results showed that the relationships between tree species, tree density, basal area at D. B. H, and height class (or diameter class) could be simulated by different equations. There was a significant positive correlation between tree species and tree density for different height class or different D. B. H. class. The structure dynamic analysis showed that the community of Tsoongiodendron odorum Chun was very unstable, and the species sharing degree in four communities was fairly lower, indicating that the dominant species were very obvious. The results could give a useful clue for the studies on endangered mechanism of rare species.  相似文献   

9.
Phylogenetic relationships of the different species in the genus Dendranthema (DC.) Des Moul. were estimated based on chromosome fluorescent in situ hybridization (FISH) with 18S-26S rDNA of Arabidopsis and genomic DNA of Dendranthema as probes. The results revealed that there was no positive correlation between the number of nuclear organization region (NOR) loci and the ploidy of Dendranthema.The exact cytogenetic information of NORs about 14 operational taxonomic units (OTUs) indicated that D.vestitum (Hemsl.) Ling et Shih was closer to the cultivars than other putative species, whereas D. zawadskii (Herb.) Tzvel. was the most distinct. The ambiguously distributed signals of genomic in situ hybridization (GISH) with genomic DNA of lower ploidy species as probes suggested that different genomes among Dendranthema were mixed. The result also indicated the limitation of GISH in studies on the phylogenetic relationships of the different species in this genus Dendranthema and on the origin of cultivated chrysanthemums. Based on these results and previous research, the origin of Chinese cultivated chrysanthemum is discussed.  相似文献   

10.
To determine the level of microsatellite sequence differences and to use the information to construct a phylogenetic relationship for cultivated tetraploid cotton (Gossypium spp.) species and their putative diploid ancestors, 10 genome-derived microsatellite primer pairs were used to amplify eight species, including two tetraploid and six diploid species, in Gossypium. A total of 92 unique amplicons were resolved using polyacrylamide gel electrophoresis. Each amplicon was cloned, sequenced, and analyzed using standard phylogenetic software. Allelic diversities were caused mostly by changes in the number of simple sequence repeat (SSR) motif repeats and only a small proportion resulted from interruption of the SSR motif within the locus for the same genome. The frequency of base substitutions was 0.5%-1.0% in different genomes, with only few indels found. Based on the combined 10 SSR flanking sequence data, the homology of A-genome diploid species averaged 98.9%, even though most of the amplicons were of the same size, and the sequence homology between G. gossypioides (Ulbr.) Standl. and three other D-genome species (G. raimondii Ulbr., G. davidsonii Kell., and G. thurberi Tod.) was 98.5%, 98.6%, and 98.5%, respectively. Phylogenetic trees of the two allotetraploid species and their putative diploid progenitors showed that homoelogous sequences from the A- and D-subgenome were still present in the polyploid subgenomes and they evolved independently. Meanwhile, homoelogous sequence interaction that duplicated loci in the polyploid subgenomes became phylogenetic sisters was also found in the evolutionary history of tetraploid cotton species. The results of the present study suggest that evaluation of SSR variation at the sequence level can be effective in exploring the evolutionary relationships among Gossypuim species.  相似文献   

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In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980.  相似文献   

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Shapes of curves of pH-dependence of reactions   总被引:14,自引:14,他引:0  
A simple case is considered in which the rate of a two-step reaction depends on pH because the intermediate formed in the first step has to gain (or lose) a proton before it can react in the second step, and in which the rate-determining step therefore changes with pH. The curves of reaction rate against pH are shown to be symmetrical, and the sharpest peak possible has a width at half its height of 1.53pH units, i.e. of 2log(3+2 radical2). Any particular curve for this situation proves to be identical with a curve that could be generated for the pH-dependence of a single-step reaction in which the rate is proportional to the concentration of a particular ionic form of a reactant. Curves for the latter situation, however, can have forms impossible for the former case in which the rate-determining step changes, but only if the protonations that activate and deactivate the reactant are co-operative. The peak can then become even sharper, and its width at half its height can fall to 1.14pH units, i.e. to 2log(2+ radical3).  相似文献   

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Dietary intakes of tomatoes and tomato products containing lycopene have been shown to be associated with decreased risk of chronic diseases such as cancer and cardiovascular diseases in numerous studies. Serum and tissue lycopene levels have also been inversely related to the risk of lung and prostate cancers. Lycopene functions as a very potent antioxidant, and this is clearly a major important mechanism of lycopene action. In this regard, lycopene can trap singlet oxygen and reduce mutagenesis in the Ames test. However, evidence is accumulating for other mechanisms as well. Lycopene at physiological concentrations can inhibit human cancer cell growth by interfering with growth factor receptor signaling and cell cycle progression specifically in prostate cancer cells without evidence of toxic effects or apoptosis of cells. Studies using human and animal cells have identified a gene, connexin 43, whose expression is upregulated by lycopene and which allows direct intercellular gap junctional communication (GJC). GJC is deficient in many human tumors and its restoration or upregulation is associated with decreased proliferation. The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibits a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression in the HL-60 promyelocytic leukemia cell line, suggesting some interaction at a nuclear or subcellular level. The combination of lycopene and lutein synergistically interact as antioxidants, and this may relate to specific positioning of different carotenoids in membranes. This review will focus on the growing body of evidence that carotenoids have unexpected biologic effects in experimental systems, some of which may contribute to their cancer preventive properties in models of carcinogenesis. Consideration of solubility in vitro, comparison with doses achieved in humans by dietary means, interactions with other phytochemicals, and other potential mechanisms such as stimulation of xenobiotic metabolism, inhibition of cholesterogenesis, modulation of cyclooxygenase pathways, and inhibition of inflammation will be considered. This review will point out areas for future research where more evidence is needed on the effects of lycopene on the etiology of chronic disease.  相似文献   

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