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  1. No Access

    Article

    Action of Deoxyribonuclease on Lampbrush Chromosomes

    UNTIL a few years ago it was generally assumed that nucleic acids lack the diversity required of primary genetic material, and proteins alone were supposed to possess this attribute. The results of early studi...

    H. G. CALLAN, H. C. MACGREGOR in Nature (1958)

  2. No Access

    Article

    Gene Amplification in the Oocyte Nucleus of Mutant and Wild-type Xenopus laevis

    DURING the development of the amphibian oocyte, the germinal vesicle becomes enlarged and can be seen to contain very many nucleoli1,2 instead of the four which would be expected from the tetraploidy of the egg n...

    EVA PERKOWSKA, H. C. MACGREGOR, M. L. BIRNSTIEL in Nature (1968)

  3. No Access

    Article

    The chromosomal localization of a heavy satellite DNA in the testis of Plethodon c. cinereus

    When DNA from blood or liver of Plethodon c. cinereus is centrifuged to equilibrium in cesium chloride it separates out into 2 components. The smaller or satellite component is relatively rich in G + C and is the...

    H. C. Macgregor, James Kezer in Chromosoma (1971)

  4. No Access

    Article

    A fresh look at meiosis and centromeric heterochromatin in the red-backed salamander, Plethodon cinereus cinereus (Green)

    Male meiosis, with special regard to the centromeric heterochromatin and to centromeric structure, has been studied in the salamander, Plethodon cinereus cinereus. In this salamander, n = 14. Early meiotic propha...

    James Kezer, H. C. Macgregor in Chromosoma (1971)

  5. No Access

    Article

    Interlocking and knotting of ring nucleoli in amphibian oocytes

    Various configurations of interlocking and knotting of ring nucleoli from amphibian oocytes have been identified in material taken from 2 females of Eurycea bislineata and one female of Plethodon cinereus. The si...

    H. C. Macgregor, Marcela Vlad in Chromosoma (1972)

  6. No Access

    Article

    The arrangement of chromosomes in nuclei of sperm from plethodontid salamanders

    Plethodontid salamanders have n = 13 or 14 large metacentric or sub-metacentric chromosomes. Sperm nuclei from Plethodon cinereus measure 72×1 μm. The nucleoprotein of spermatids is at first finely granular. In e...

    H. C. Macgregor, Muriel H. Walker in Chromosoma (1973)

  7. No Access

    Article

    The nucleolar organizer of Plethodon cinereus cinereus (Green)

    The 7th longest lampbrush bivalent in oocytes of Plethodon cinereus cinereus has a region of attached oocyte nucleoli near to the centromere on the shorter arm of each half bivalent. When squash preparations of P...

    H. C. Macgregor, James Kezer in Chromosoma (1973)

  8. No Access

    Article

    The nucleolar organizer of Plethodon cinereus cinereus (Green)

    The lampbrush nucleolar organizers in P. c. cinereus are on the shorter arms of the 7th longest bivalent, near to the centromeres. The organizer consists of a non-chromomeric, Feulgen-negative section of the half...

    James Kezer, H. C. Macgregor in Chromosoma (1973)

  9. No Access

    Article

    Observations on centromeric heterochromatin and satellite DNA in salamanders of the genus Plethodon

    DNA from Plethodon cinereus cinereus separates into two fractions on centrifugation to equilibrium in neutral CsCl. The smaller of these fractions has been described as a high-density satellite. It represents abo...

    H. C. Macgregor, Heather Horner, C. A. Owen, I. Parker in Chromosoma (1973)

  10. No Access

    Article

    Chromomere number and its genetic significance in lampbrush chromosomes

    The chromosomes of three species of salamander belonging to the genus Plethodon have been studied with regard to the absolute length of the haploid set of lampbrush chromosomes and the number and distribution of ...

    Marcela Vlad, H. C. Macgregor in Chromosoma (1975)

  11. No Access

    Article

    In situ hybridization of ribosomal DNA labelled with 125iodine to metaphase and lampbrush chromosomes from newts

    Methods are described for in situ hybridization of ribosomal DNA from Xenopus laevis, labelled in vitro with 125iodine, to mitotic and lampbrush chromosomes from Triturus cristatus carnifex. The hybridization rea...

    Sally Hennen, S. Mizuno, H. C. Macgregor in Chromosoma (1975)

  12. No Access

    Article

    In situ hybridization of “Nick-translated” 3H-ribosomal DNA to chromosomes from salamanders

    A technique is described for preparation of 3H-labelled DNA by nick-translation employing deoxyribonuclease I and DNA polymerase I. The labelled DNA can be obtained in high yield with specific activities of 106 c...

    H. C. Macgregor, S. Mizuno in Chromosoma (1976)

  13. No Access

    Article

    Chromosomes, DNA sequences, and evolution in salamanders of the genus Aneides

    Chromosomes and DNA sequence homologies have been studied in salamanders of the genus Aneides. The species studied included A. ferreus, flavipunctatus, lugubris, hardii and aeneus. All species have 14 chromosomes...

    H. C. Macgregor, Christine Jones in Chromosoma (1977)

  14. No Access

    Article

    The arrangement and transcription of “middle repetitive” DNA sequences on lampbrush chromosomes of Triturus

    Nick-translated 3H middle repetitive DNA (C0t 0.2–50) from Triturus cristatus carnifex was in situ hybridized to RNA transcripts on the loops of lampbrush chromosomes and to the denatured DNA in mitotic chromosom...

    H. C. Macgregor, Christine Andrews in Chromosoma (1977)

  15. No Access

    Article

    In situ hybridization of highly repetitive DNA to chromosomes of Triturus cristatus

    Highly repetitive DNA of C0t 0–0.2 was purified from whole DNA of Triturus cristatus carnifex, labelled by nick translation, and in situ hybridized to RNA transcripts on the loops of lampbrush chromosomes and to ...

    H. C. Macgregor in Chromosoma (1979)

  16. No Access

    Chapter

    The Transcription of Satellite and Ribosomal DNA Sequences on Lampbrush Chromosomes of Crested Newts

    Over the past few years we have asked specifically with regard to lampbrush chromosomes of crested newts, how certain classes of DNA sequences are arranged and expressed and how, if at all, their arrangement r...

    H. C. Macgregor, J. M. Varley, G. T. Morgan in International Cell Biology 1980–1981 (1981)

  17. No Access

    Chapter and Conference Paper

    The Transcription of Satellite and Ribosomal DNA Sequences on Lampbrush Chromosomes of Crested Newts

    Over the past few years we have asked specifically with regard to lampbrush chromosomes of crested newts, how certain classes of DNA sequences are arranged and expressed and how, if at all, their arrangement r...

    H. C. Macgregor, J. M. Varley, G. T. Morgan in International Cell Biology 1980–1981 (1981)

  18. No Access

    Article

    Ribosomal gene amplification in multinucleate oocytes of the egg brooding hylid frog Flectonotus pygmaeus

    The multinucleate oocytes of Flectonotus pygmaeus begin as cysts containing 2,000 or more meiotic nuclei. Each nucleus amplifies its ribosomal DNA early in oogenesis. The level of amplification is widely differen...

    H. C. Macgregor, Eugenia M. del Pino in Chromosoma (1982)

  19. No Access

    Chapter

    The evolutionary consequence of major genomic changes in Amphibia

    It seems appropriate to begin this discussion by examining the kinds of major genomic changes that have happened in the course of amphibian evolution, and to segregate those that may have been expected to cont...

    H. C. Macgregor in Chromosomes Today (1984)

  20. No Access

    Chapter

    Abstracts of Selected Posters

    The analysis of chromosomes of mouse embryos permits detection of transmitted chromosome damage. The protocol involves the treatment of one parent (usually the male) with a clastogen, recovery of embryos and p...

    R. Albanese, J. L. Antoine, B. Dutrillaux, T. Ashley, L. Avivi… in Chromosomes Today (1984)

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