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  • 1
    Electronic Resource
    Electronic Resource
    Similarity in karyotypes ofRattus rattus with 38 chromosomes from India and other parts of the world (1972)
    Springer
    Cellular and molecular life sciences 28 (1972), S. 1375-1377 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Chromosomen von 12 Männchen und 12 Weibchen vonRattus rattus wroughtoni sowie 2 Weibchen vonRattus rattus wurden untersucht und es wurden überall 38 Chromosomen gefunden, verursacht durch Robertsonische Verbindung von 4 akrozentischen Paaren vonRattus rattus mit 42 Chromosomen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01965355
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  • 2
    Electronic Resource
    Electronic Resource
    Factors influencing replicon organization in tissues having different S-phase durations in the mole rat, Bandicota bengalensis (1987)
    Springer
    Chromosoma 95 (1987), S. 285-289 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In order to identify factors affecting the length of S-phase in mammals, DNA fibre autoradiograms from different tissues [bone marrow, phytohaemagglutinin (PHA)-stimulated spleen lymphocytes and whole body cells of new-borns] of the mole rat, Bandicota bengalensis, were examined for various parameters of replicon organization. The duration of S-phase in bone marrow and spleen was 12–14 h while that in new-borns was 8–9 h. Fork migration rate was significantly greater in new-borns than in bone marrow, and replicon size was significantly smaller in newborns than in spleen. Thus it appears that several factors contribute, to varying degrees, in establishing the duration of S-phase in any cell type. In about 20% of the replicon clusters, constituent replicons were found to initiate replication asynchronously. This asynchronous initiation could possibly be due to an effect of transcription on time of initiation since it is likely that neighbouring replicons would be transcribed to different extents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294785
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  • 3
    Electronic Resource
    Electronic Resource
    Chromosome condensation and Hoechst 33258 fluorescence in meiotic chromosomes of the grasshopper Spathosternum prasiniferum (Walker) (1979)
    Springer
    Chromosoma 70 (1979), S. 251-258 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Patterns of Hoechst 33258 fluorescence have been studied in grasshopper chromosomes. At metaphase of mitotic as well as meiotic divisions — when chromosomes were maximally compact — all the chromosomes fluoresced brightly but no differentially fluorescing regions were detected. However, when all the chromosomes, except the X, were highly extended at pachytene and diplotene stages a distinct differential fluorescence was observed: only the centromeres of the autosomal bivalents fluoresced brightly whereas the entire X univalent showed bright fluorescence. Restriction of differentially bright fluorescence to the more condensed regions of chromosomes suggests a modulatory role for chromosome condensation in the production of Hoechst fluorescence. This suggestion was further strengthened by the substantial quenching of fluorescence caused by removal of chromosomal proteins following treatment with H2SO4. Similarly, post-C-band-treatment staining with Hoechst also led to quenching, though now the centromeres of the chromosomes, including the X, retained their differential fluorescence. It is proposed, therefore, that in grasshopper chromosomes, H-fluorescence is modulated by chromosome condensation brought about by differential ratios of DNA/protein at different chromosome regions and at different division stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288409
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  • 4
    Electronic Resource
    Electronic Resource
    Variation of constitutive heterochromatin in the sex chromosomes of the rodent Bandicota bengalensis bengalensis (Gray) (1973)
    Springer
    Chromosoma 41 (1973), S. 75-84 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bandicota bengalensis bengalensis (Gray) trapped from different localities of India and Nepal exhibited a marked variation in the size and morphology of sex chromosomes. Three types of X's were found; A) simple acrocentric, B) composite subtelocentric and C) composite submetacentric X with their relative sizes 5.9%, 7.5% and 9.6% of the genome respectively. The autosomes remained unaltered. It was shown that this variation in the size of sex chromosomes was caused by deletion of constitutive heterochromatin. The Y chromosome was also found to be variable. Usually a large X was combined with a large Y. The preponderance of homozygotes for each type of X chromosome in populations, suggested the probable role of sex chromosomes heterochromatin in speciation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284075
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  • 5
    Electronic Resource
    Electronic Resource
    Identification and patterns of synapsis of the autosomally translocated Y-chromosome of the Indian mongoose, Herpestes auropunctatus (Hodgson) (1982)
    Springer
    Chromosoma 87 (1982), S. 477-489 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The multiple sex chromosome system, X1X2Y ♂/X1X1X2X2♀, in the small Indian mongoose, Herpestes auropunctatus, results from a translocation of a part of Y chromosome to an autosome. It is not possible to distinguish the autosome which harbours the Y chromosome element in the somatic complement. By employing the surface-spreading technique to prophase I meiocytes we have identified the region to which the Y chromosome has been translocated as the short arm of chromosome 9 which is a subtelocentric chromosome. This Y chromosome component lacks heterochromatin and no sex vesicle is organised during meiotic prophase. This suggests to us that Y heterochromatin in mammals may be required for the production of a sex vesicle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333469
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  • 6
    Electronic Resource
    Electronic Resource
    Mammalian sex chromosomes (1986)
    Springer
    Chromosoma 93 (1986), S. 367-374 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The X and Y chromosomes of the musk shrew are the two largest in the complement and they regularly form a single chiasma during meiosis. This chiasma is located in the short arms of the X and Y, both of which show partial C-banding at meiosis. The in vitro incorporation of 5-bromodeoxyuridine/tritiated thymidine during late S reveals that the non-C-band region of the Y finishes replication later than the C-band positive heterochromatin. During meiosis, the sex bivalent opens out early in pachytene to reveal a single chiasma which persists until late metaphase-I. In surface-spread, silver-stained meiocytes, the sex bivalent morphology changes from a phase of extensive pairing to one which includes a visible chiasma through a brief diffuse stage. Observations on C-banded meiocytes show a shift in the sex pair from a C-band positive to a negative state as compared to their corresponding somatic pattern. Comparable changes are also observed in the sex bivalents of other mammals which undergo a chiasmatic exchange. This suggests that in addition to pairing homology, an alteration in the chromatin configuration may be necessary for crossing over to occur between the sex chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327596
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  • 7
    Electronic Resource
    Electronic Resource
    DNA replication, G- and C-bands and meiotic behaviour of supernumerary chromosomes of Rattus rattus (Linn.) (1974)
    Springer
    Chromosoma 45 (1974), S. 111-119 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Supernumerary chromosomes have been observed in a few individuals of three subspecies of Rattus rattus from India and Nepal. The supernumerary chromosomes are late replicating and positively heteropycnotic during meiosis which characterize their heterochromatic nature. Their G-banding patterns do not exactly resemble the patterns exhibited by the chromosomes of similar size and morphology of the normal complement. The supernumerary chromosomes become conspicuous for the lack of a centromeric C-band in them as compared to the prominent C-bands in other chromosomes of the complement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283834
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  • 8
    Electronic Resource
    Electronic Resource
    Male-biased distribution of the human Y chromosomal genes SRY and ZFY in the lizard Calotes versicolor, which lacks sex chromosomes and temperature-dependent sex determination (1997)
    Springer
    Chromosome research 5 (1997), S. 413-419 
    Details
    ISSN: 1573-6849
    Keywords: evolution ; reptiles ; sex determination ; SRY ; ZFY
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present investigation on the lizard Calotes versicolor, which lacks temperature-dependent sex determination, all the conventional cytological techniques used failed to resolve a distinguishable pair of sex chromosomes. However, probing of the genome with the human Y-linked genes SRY and ZFY showed sex-specific bias in their distribution. While the SRY probe hybridized to all the males, more than half of the females examined did not show any hybridization. ZFY hybridized to both the sexes, giving two bands; one was common to all the individuals of both sexes, but the other, of the lower molecular length, occurred in all the males but in less than 50% of females. This predominantly male-specific band is named AMF. The SRY-positive females were also positive for the AMF of ZFY. As positive as well as negative females were fertile and none of the males lacked SRY, it appears that SRY is essential for males only and that both the genes are syntenic in this species. This report raises interesting possibilities on the differentiation of the sex chromosomes in C. versicolor and evolution of SRY/ZFY on the Y chromosome of eutherian mammals through the ancestral group(s) that harbour sex-independent SRY- and ZFY-related genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018452526903
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  • 9
    Electronic Resource
    Electronic Resource
    Heterogeneity in distribution of constitutive heterochromatin in four species of birds (1978)
    Springer
    Genetica 48 (1978), S. 61-65 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125287
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  • 10
    Electronic Resource
    Electronic Resource
    Mammalian sex chromosomes III. Activity of pseudoautosomal steroid sulfatase enzyme during spermatogenesis inMus musculus (1991)
    Springer
    Somatic cell and molecular genetics 17 (1991), S. 429-433 
    Details
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Parallel to the inactivation of the X chromosome in somatic cells of female, the male X in mammals is rendered inactive during spermatogenesis. Pseudoautosomal genes, those present on the X-Y meiotically pairable region of male, escape inactivation in female soma. It is suggested, but not demonstrated, that they may also be refractory to the inactivation signal in male germ cells. We have assayed activity of the enzyme steroid sulfatase, product of a pseudoautosomal gene, in testicular cells of the mouse and shown its presence in premeiotic, meiotic (pachytene), and postmeiotic (spermatid) cell types. It appears that, as in females, pseudoautosomal genes may escape inactivation in male germ cells also.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01233166
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