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  • 1
    Electronic Resource
    Electronic Resource
    The distribution of genes on chromosomes: A cytological approach (1993)
    Springer
    Journal of molecular evolution 37 (1993), S. 117-122 
    Details
    ISSN: 1432-1432
    Keywords: Chromosomes ; Human chromosomes ; Gene distribution ; DNase I hypersensitivity ; CpG islands ; In situ nick translation ; Inactive X chromosome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies during the last 20 years have shown that the chromosomes of many organisms, especially those of higher vertebrates, consist of a series of segments having different properties. These can be recognized as, for example, G- and R-bands. Recent studies have indicated that genes tend to lie in the R-bands rather than in the G-bands, although the number of genes that has been mapped with high precision is, as yet, only a very small proportion of the total, probably much less than 1%. We have therefore sought to study the distribution of genes on chromosomes using a cytological approach in conjunction with “universal” markers for genes. Such markers include mRNA and the gene-rich, G + C-rich H3 fraction of DNA, both of which can be localized using in situ hybridization, and DNase I hypersensitivity, and digestion by restriction enzymes known to show selectivity for the CpG islands associated with active genes, both of which can be detected using in situ nick translation. We have chosen to use the approaches involving in situ nick translation and have shown that the patterns of DNase I hypersensitivity and of CpG islands on human chromosomes show a strict correspondence to R-banding patterns: Deviations from R-banding patterns reported by previous investigators who have made similar studies appear to be attributable to excessive digestion. On the other hand, we have not found the expected differentiation between the active and inactive X chromosomes; this may perhaps be attributable to such factors as the demethylation of some non-island CpGs in the inactive X and the possible alterations of chromatin structure caused by methanol-acetic-acid fixation affecting DNase I hypersensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407346
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  • 2
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of mammalian chromosomes from prophase to telophase (1991)
    Springer
    Chromosoma 100 (1991), S. 410-418 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Changes in the morphology of human and murine chromosomes during the different stages of mitosis have been examined by scanning electron microscopy. Two important findings have emerged from this study. The first is that prophase chromosomes do not become split into pairs of chromatids until late prophase or early metaphase. This entails two distinct processes of condensation, the earlier one starting as condensations of chromosomes into chromomeres which then fuse to form a cylindrical body. After this cylindrical body has split in two longitudinally, further condensation occurs by mechanisms that probably include coiling of the chromatids as well as other processes. The second finding is that the centromeric heterochromatin does not split in two at the same time as the rest of the chromosome, but remains undivided until anaphase. It is proposed that the function of centromeric heterochromatin is to hold the chromatids together until anaphase, when they are separated by the concerted action of topoisomerase II acting on numerous similar sites provided by the repetitive nature of the satellite DNA in the heterochromatin. A lower limit to the size of blocks of centromeric heterochromatin is placed by the need for adequate mechanical strength to hold the chromatids together, and a higher limit by the necessity for rapid splitting of the heterochromatin at anaphase. Beyond these limits malsegregation will occur, leading to aneuploidy. Because the centromere remains undivided until anaphase, it cannot undergo the later stage of condensation found in the chromosome arms after separation into chromatids, and therefore the centromere remains as a constriction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337519
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  • 3
    Electronic Resource
    Electronic Resource
    Electron microscopy of the parameres formed by the centromeric heterochromatin of human chromosome 9 at pachytene (1986)
    Springer
    Chromosoma 94 (1986), S. 199-204 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The structure and arrangement of the parameres, which are small bodies representing part of the heterochromatin of human chromosome 9 at pachytene, were studied using transmission and scanning electron microscopy. Parameres appear to be denser than other parts of the chromosomes but have a similar fibrous substructure. The most common arrangement is clusters on the axis of the bivalent, consisting of varying numbers of parameres of variable size. The parameres are joined to each other and to the rest of the chromosome by interconnecting fibres. No evidence was obtained for the organisation of parameres into paired lateral loops, as proposed by previous workers using light microscopy. The combination of osmium impregnation of pachytene chromosomes with a backscattered electron detector in the scanning electron microscope produced very clear images of the pattern of chromomeres. This procedure may prove valuable for pachytene mapping of chromosomes because of the greatly improved resolution compared with light microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288494
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  • 4
    Electronic Resource
    Electronic Resource
    Frequency of Polyploid Spermatozoa in Man (1971)
    [s.l.] : Nature Publishing Group
    Nature 231 (1971), S. 49-49 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Table 1 Characteristics of the Sperm Samples used and Frequency of Polyploid Sperm Sperm count * Sperm Sperm Number Number Number % Polyploid Subject Age x 10 ml. motility *(%) morphology * of sperm diploid tetraploid % normal measured 1 Data not ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/231049a0
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  • 5
    Electronic Resource
    Electronic Resource
    Mechanisms of quinacrine binding and fluorescence in nuclei and chromosomes (1986)
    Springer
    Histochemistry and cell biology 84 (1986), S. 566-574 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mechanism has been investigated whereby quinacrine binds to the DNA of nuclei and chromosomes in cytological preparations fixed in methanol-acetic acid. A variety of evidence is consistent with the idea that the quinacrine binds by intercalation. This is supported by a high value for the affinity of quinacrine for DNA, together with a saturation value of 0.2 quinacrine molecules/nucleotide; binding in the presence of strong salt solutions; and inhibition of fluorescence and banding by denaturation or depurination of DNA. At high quinacrine concentrations, weak binding of quinacrine to nuclei and chromosomes also occurs, but this is not relevant to the production of strong fluorescence or Q-banding patterns. A number of factors were tested which might have affected quinacrine fluorescence and banding. These included: pH; blocking protein amino groups by acetylation or benzoylation; introduction of hydrophobic groups by benzoylation; and dephosphorylation. All these treatments were without effect. However, comparison of the quinacrine fluorescence of human and onion nuclei, which differ substantially in the base composition of their DNa, shows that quinacrine fluorescence can be enhanced in cytological preparations by AT-rich DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00482993
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  • 6
    Electronic Resource
    Electronic Resource
    Nuclear phenomena and development (1977)
    [s.l.] : Nature Publishing Group
    Nature 270 (1977), S. 455-455 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE illustration on the jacket of this book of Balbiani rings on a polytene chromosome seems particularly appropriate for the subject of Nuclear Cytology in Relation to Development. In fact, Professor d'Amato takes his subject matter from a much wider field than this illustration might suggest. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/270455a0
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  • 7
    Electronic Resource
    Electronic Resource
    Restriction endonuclease/nick translation of fixed mouse chromosomes: A study of factors affecting digestion of chromosomal DNA in situ (1991)
    Springer
    Chromosoma 100 (1991), S. 203-211 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We used a restriction endonuclease/nick translation procedure to study the ability of certain enzymes, known to cleave mouse satellite DNA in solution, to attack satellite DNA in fixed mouse chromosomes. Although AvaII and Sau96I readily attack the mouse major satellite in fixed chromosomes, BstNI and EcoRII do not normally do so, although if the heterochromatin is uncondensed as a result of culture in the presence of 5-azacytidine, BstNI can attack it. No clear evidence was obtained for digestion in situ of the minor satellite of mouse chromosomes by MspI, the only enzyme reported to cleave this satellite. Our results show that the DNA of mouse heterochromatin is not merely not extracted by certain restriction enzymes, but is actually not cleaved by them. Chromatin conformation is therefore shown to be an important factor in determining patterns of digestion of chromosomes by restriction endonucleases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337249
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  • 8
    Electronic Resource
    Electronic Resource
    Cytological mapping of human chromosomes: results obtained with Quinacrine fluorescence and the Acetic-Saline-Giemsa techniques (1971)
    Springer
    Chromosoma 35 (1971), S. 310-325 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The similarities and differences between the banding patterns obtained in human chromosomes with the Quinacrine fluorescence and the Acetic-Saline-Giemsa (ASG) techniques are described. The use of these techniques to identify each chromosome pair in the human karyotype is discussed, as also is the use of the methods to identify aberrant chromosomes and to map points of exchange in translocations and inversions. A number of examples are used to illustrate the resolution permitted by these new methods. Seven polymorphic regions on normal chromosomes are described, which include four identified by fluorescence on chromosomes 3,4, 13, and 22. The secondary constrictions on chromosomes 1, 9, and 16, which had previously been observed in conventionally stained preparations from favourable material, are particularly clear in all cells treated with the Giemsa techniques. The new methods make it possible to detect small differences in size between the heterochromatic blocks at these regions in homologous chromosomes. The benefit to human genetics of studying the familial segregation of both structurally rearranged and normal, but polymorphic chromosomes, where the chromosomes or parts of chromosomes can be unambiguously identified is stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326281
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  • 9
    Electronic Resource
    Electronic Resource
    The distribution of quinacrine on chromosomes as determined by X-ray microanalysis (1981)
    Springer
    Chromosoma 82 (1981), S. 717-734 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The distribution of quinacrine in relation to Q-banding on CHO chromosomes has been investigated using X-ray microanalysis. Technical problems involved in this type of experiment were studied in detail. It was necessary to use a solution of quinacrine acetate in acetic acid to ensure that the only chlorine detectable in quinacrine-stained chromosomes was in the quinacrine molecule. Electron irradiation during analysis rapidly destroys quinacrine fluorescence, but the chlorine is not lost from the chromosomes, and there are several reasons for supposing that a reliable distribution of quinacrine on the chromosome can be obtained by the method. — Small variations along the chromosome in the amounts of chlorine (representing quinacrine) and of phosphorus (mainly DNA) occur. The distribution patterns for chlorine and phosphorus show a good resemblance to each other for each homologous chromosome; quinacrine fluorescence patterns (Q-bands) do not resemble chlorine distribution patterns, however. The results of this study therefore support the view that Q-bands result from the differential quenching of fluorescence along chromosomes to which the quinacrine is essentially uniformly bound, and do not reflect differential binding of quinacrine along the chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285777
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  • 10
    Electronic Resource
    Electronic Resource
    Relative DNA contents of somatic nuclei of ox, sheep and goat (1976)
    Springer
    Chromosoma 57 (1976), S. 171-175 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Diploid ox nuclei contain about 14% more DNA than nuclei from sheep of the same sex. Goat nuclei have a similar DNA content to those of sheep. In view of the similar chromosome banding patterns in these species, it appears that chromosome evolution must have involved numerous minute interstitial deletions or additions of DNA. Although chromosomes which have similar banding patterns in these three species may be regarded as homologous in this respect, and can be regarded as having a common evolutionary origin, they are not homologous for the quantity of their DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292915
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