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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 435 (1984), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 69 (1978), S. 255-264 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ribosomal RNA cistron numbers in all the seven primary trisomics of diploid barley (Hordeum vulgare L.) were determined by DNA-rRNA filter hybridisation. Trisomies for the nucleolus organiser (NO) chromosomes 6 and 7 showed the highest levels of rDNA (DNA complementary to rRNA) indicating the localisation of rRNA cistrons on the NOs. Chromosomes 6 and 7 possessed 1,580 and 2,690 rRNA (18S + 5.8S + 26S) cistrons respectively. Trisomics for the other chromosomes (except for 3) also displayed levels of rDNA significantly higher (22–32%) than the diploid controls although the dosage of NOs was not altered. These non-specific increases were also present in trisomics for 6 and 7 (NOs) which showed further increases equivalent to their respective contributions. The nonspecific increases due to trisomy is indicative of rDNA compensation. Such increases did not persist in diploid sibs of the trisomics, demonstrating the nonheritable nature of the compensation.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 66 (1978), S. 185-192 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Meiotic chromosome behaviour was studied in the hexaploid Hordeum parodii (2n=6x=42) and in six haploids (2n=3x=21) obtained from a cross between H. parodii and H. bulbosum (2n=2x=14) whereby all bulbosum chromosomes were selectively eliminated. The alloploid nature of H. parodii was evident from the exclusive bivalent formation at the hexaploid level and the low and variable number of bivalents in its haploid derivatives. In haploids, both nonhomologous (intragenomic) and homoeologous (intergenomic) chromosomes paired at prophase. Foldbacks in single chromosomes, bivalents and trivalents were observed at prophase and metaphase I. At diakinesis, the associations involved a maximum of 20 chromosomes which decreased to 12 by metaphase I. This decrease was attributed to the failure of the non-homologous associations to persist until metaphase I. A “hemizygous-ineffective” control for the diploid-like behaviour of the hexaploid parodii is proposed to explain the homeologous chromosome pairing in its haploid derivatives.
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  • 4
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cytological observations were made on embryo and endosperm tissues with different genome combinations that were produced by crossing the diploid and tetraploid cytotypes of Hordeum vulgare and H. bulbosum. The high frequency of barley haploids results from hybridization followed by the selective elimination of bulbosum chromosomes during the early development of embryos which initially contained a ratio of 1 vulgare to 1 bulbosum genomes. Elimination is gradual as indicated by the increase in the percentage of cells with the gametic chromosome number. However, the balance between genetic factors of the two parents appears to regulate the stability or elimination of chromosomes. Triploid embryos containing 1 vulgare to 2 bulbosum genomes are relatively stable. The most stable endosperm tissues examined had a ratio of 1 vulgare to 4 bulbosum genomes. Evidence of genetic control in both the vulgare and bulbosum chromosomes and their interaction is discussed. As has been suggested by Lange (1971) and also found in mammalian somatic cell hybrids, the most probable basis for selective chromosome elimination relates to mitotic rhythm and the duration of cell cycle phases.
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  • 5
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The interspecific hybrids of Hordeum exhibit selective suppression of secondary constriction formation in the chromosome(s) contributed by one of the two parents. A comparison of the number of SAT (secondary constriction) chromosomes in the metaphase cells and the maximum number of nucleoli in interphase cells revealed that the chromosomes capable of organising nucleoli were not always reflected through secondary constriction formation. — The rDNA (DNA complementary to rRNA) amounts were estimated by DNA-rRNA filter hybridisation in diploid and polyploid species of Hordeum and their hybrids. While similar rDNA proportions were present in diploid and autotetraploid lines of H. bulbosum, there were up to threefold differences between H. vulgare and allohexaploids. Furthermore, differences were also apparent between species of same ploidy level. Ribosomal RNA (18S+5.8S+26S) cistron numbers in each of the five experimental hybrids exhibiting the selective suppression of secondary constriction formation revealed no selective loss of rDNA. — The presence of a higher number of nucleoli than the number of SAT chromosomes seen and the presence of expected number of rRNA cistrons suggest that the suppression of secondary constriction formation is not due to selective loss of rDNA.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 73 (1986), S. 31-39 
    ISSN: 1432-2242
    Keywords: Ag+-Cs2SO4 gradient ; Buoyant density ; Cryptic satellites in situ hybridization ; Thermal denaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three satellites on the heavy side of the main band and two satellites on the light side were isolated in a pure from by preparative ultracentrifugation of H. vulgare DNA in Ag+/Cs2SO4 density gradients. The satellites were characterised in terms of their buoyant densities in CsCl and their thermal dissocation temperature in both native and reassociated forms to Cot 4. In CsCl gradients, heavy satellites formed a single peak whereas light satellites resolved into more than one component. Thermal transitions of some satellites indicated the presence of more than one molecular species. The multicomponent nature of thermal denaturation profiles was evident on differential analysis. Radioactive RNAs complementary to the three heavy satellites of H. vulgare were localised by in situ hybridization onto its nuclei and chromosomes. One heavy satellite (H3) was found to be distributed on all chromosomes, although one pair showed less hybridization compared to the others. The other satellite (H1) appeared to be present in a much lower amount on the chromosomes.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 73 (1986), S. 40-46 
    ISSN: 1432-2242
    Keywords: DNA characterization ; Cryptic satellites ; Cytological localization ; Buoyant density ; Thermal denaturation ; Hordeum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three satellites, one (H1) on the heavy side of the main band of Hordeum arizonicum DNA and two (L1, L2) on the lighter side were purified using preparative silver-cesium sulphate density gradients. The native and the reassociated satellite DNAs were analysed in terms of buoyant densities and thermal dissociation. In cesium chloride gradients the H1 and L1 satellites formed single peaks corresponding to buoyant densities of 1.700 and 1.701 g · cm−3 respectively while the L2 satellite gave two peaks (1.680 and 1.661 g · cm−3). The H1 satellite showed three thermal components (Tm=82.5 °C, 87 °C and 91.5 °C) while the L1 and L2 had three (86.5, 92, 97.5 °C) and two (86, 95 °C) respectively. The H1 satellite was localized on the nuclei and chromosomes. The distribution of H1 onto approximately on third of the complement may reflect the genome specific origin of this satellite.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 88 (1994), S. 441-448 
    ISSN: 1432-2242
    Keywords: RFLP ; Mitochondrial DNA ; Cytoplasmic male sterility ; Pearl millet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial DNA (mtDNA) from 13 cytoplasmic male-sterile (cms) lines from diverse sources were characterized by Southern blot hybridization to pearl millet and maize mtDNA probes. Hybridization patterns of mtDNA digested with PstI, BamHI, SmaI or XhoI and probed with 13.6-, 10.9-, 9.7- or 4.7-kb pearl millet mtDNA clones revealed similarities among the cms lines 5141 A and ICMA 1 (classified as the S-A1 type of cytoplasm based on fertility restoration patterns), PMC 30A and ICMA 2. The remaining cms lines formed a distinct group, within which three subgroups were evident. Among the maize mitochondiral gene clones used, the coxI probe revealed two distinct groups of cytoplasms similar to the pearl millet mtDNA clones. The atp9 probe differentiated the cms line 81 A4, derived from P. glaucum subsp. monodii, while the coxII gene probe did not detect any polymorphism among the cms lines studied. MtDNA digested with BamHI, PstI or XhoI and hybridized to the atp6 probe revealed distinct differences among the cms lines. The maize atp6 gene clone identified four distinct cytoplasmic groups and four subgroups within a main group. The mtDNA fragments hybridized to the atp6 gene probe with differing intensities, suggesting the presence of more than one copy of the gene in different stoichiometries. Rearrangements involving the coxI and/or rrn18-rrn5 genes (mapped within the pearl millet clones) probably resulted in the S-A1 type of sterility. Rearrangements involving the atp6 gene (probably resulting in chimeric form) may be responsible for male sterility in other cms lines of pearl millet.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 55 (1979), S. 139-144 
    ISSN: 1432-2242
    Keywords: Chromosome elimination ; dihaploids ; Hordeum brachyantherum ; H. depressum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Interspecific crosses of Hordeum brachyantherum (2n = 28) and H. depressum (2n = 28) with H. bulbosum (2n = 14 or 28) and H. vulgare (2n = 14 or 28) were made. Crosses between brachyantherum and diploid bulbosum resulted in dihaploids (2n = 14) of brachyantherum and hybrids (2n = 21), whilst the crosses of brachyantherum by tetraploid bulbosum or vulgare gave hybrid progeny. Similarly, crosses between H. depressum and diploid bulbosum resulted in dihaploids (2n = 14) of depressum and hybrids (2n = 21), whereas depressum by tetraploid bulbosum or vulgare invariably produced hybrids. Cytological observations on 12 day old embryos obtained from these crosses revealed chromosome variability down to 14 in crosses with diploid bulbosum indicating thereby that chromosome elimination leads to haploid formation. Embryonic cells from the brachyantherum by diploid vulgare cross also exhibited a certain degree of chromosomal instability as micronuclei. The results indicate that the ratio of parental genomes in the zygote determines whether haploids or hybrids will be produced in crosses of brachyantherum or depressum with bulbosum. Furthermore, brachyantherum appears to be more efficient in eliminating bulbosum chromosomes in comparison with depressum.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 51 (1978), S. 169-175 
    ISSN: 1432-2242
    Keywords: Barley ; GA3 ; Haploids ; Nutrient Solution ; Embryo Culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Haploids from Hordeum vulgare (2n = 14) X H. Bulbosum (2n = 14) crosses result after fertilization from the subsequent elimination of bulbosum chromosomes during early embryo development. Seed set from the cross is high but embryo culture is necessary to obtain seedlings. Application of gibberellin A3 (GA3) to pollinated florets was effective for increasing the frequency of haploid seedlings produced on both nutrient-fed detached tillers and intact plants. GA3 increased both seed set and embryo yield. The number of cells per embryo during its transition to the haploid state was increased two to three times following GA3 treatments. Enhanced embryo and endosperm development was attributed to increased mitotic activity. The number of visibly differentiated embryos was doubled to about 35 % of the cultured embryos after GA3 was applied to detached tillers in nutrient solution. About 70 % of the resulting haploid plants developed from the visibly differentiated embryos. The detached tiller technique offers a convenient method of culturing haploids from field-grown plants.
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