The Japanese Journal of Genetics
Online ISSN : 1880-5787
Print ISSN : 0021-504X
ISSN-L : 0021-504X
Volume 33, Issue 2
Displaying 1-6 of 6 articles from this issue
  • Effects of X-rays on meiotic chromosomes
    Teisaku KOBAYASHI
    1958 Volume 33 Issue 2 Pages 37-41
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
    1. The present study has been made in order to compare the results with effects obtained by radiophosphorus treatment previously reported.
    2. Dormant seeds of Sesamum indicum L. were irradiated by X-rays at a dosage rate of 384.5r per minute. Doses varied from 8, 000 to 12, 000r.
    3. The frequency of chromosome aberrations observed separately at MI and AI shows a linear increase according to the dosage, and the aberration frequency at AI was usually higher than that at MI.
    4. Aberration types observed were strikingly like those induced with P32 treatments, but an inversion type was newly marked.
    5. Abnormal cleavages in tetrad stage were observed.
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  • Toshifumi TAIRA, Saburo NAWA
    1958 Volume 33 Issue 2 Pages 42-45
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
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  • Masatoshi NEI, Katsumi SYAKUDO
    1958 Volume 33 Issue 2 Pages 46-51
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
    A new method for estimating the proportion of outcrossing was developed by the use of maximum likelihood method. Using a qualitative character which is monogenically inherited, the proportion of outcrossing can be estimated in one or two generations. A numerical example was also given. Further, the outcrossing and natural crossing were differently defined.
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  • H. ONO, B. SAKAI
    1958 Volume 33 Issue 2 Pages 52-55
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
    Two intergeneric hybrids found among the natural population of Crepidiastrum Keiskeanum in Izu were studied cytologically. Simoda 4 seems to be a hybrid between C. Keiskeanum and Paraixeris denticulata. The cells with 10, 8, 7, 5 chromosomes are observed in root tips of this individual in a chimeral state. Misaki 3 considered to be a hybrid between C. keiskeanum and Lactuca squarrosa, consists of the cells with 18, 17, 15, 14 chromosomes. Not only the number of chromosomes but their karyotypes are different from cell to cell even in one individual.
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  • Susumu TAKAYAMA
    1958 Volume 33 Issue 2 Pages 56-64
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
    Recent investigations with rat ascites tumors have revealed the occurrence of a stem-lineage (or -lineages) of tumor cells which are primary contributors to the neoplastic growth, and maintain the genetic pattern of each tumor. The stem-cells are generally characterized by a very pronounced constancy with specific chromosome-number mode and by a particular ideogram which is persistent through from cell to cell by the regular mitotic behavior of the chromosomes during serial transfers. The present paper is to report the data which strongly support the stem-cell concept, by finding in the venereal tumor of a dog the existence of a population of tumor cells that are characterized by a high frequency of occurrence, and by a particular chromosome pattern.
    The chromosomes were observed in tumor cells occurring in the body fluid from the surface of the venereal tumor of a female dog with the water-pretreatment and acetic dahlia squash technique.
    Out of 146 tumor cells under study the cells containing 60 chromosomes were found at the highest frequency (32%), though frequent variations fall between 57 and 61. The ideogram of the most frequent tumor cells is characterized by the constant existence of 14 V- or J-shaped chromosomes and 46 rod-shaped ones (Figs. 11-16). It is then apparent that the most frequently occurring tumor cells which possess characteristic chromosome-number mode along with a particular ideogram from a stem-cell lineage, the members of which serve as the primary progenitors of this tumor.
    The normal somatic chromosomes of the dog were investigated in cells from the lung culture according to the roller tube method. The somatic complement comprises 77 rod-shaped elements and a large V-shaped one, the X-element (Fig. 17). The difference of the chromosome pattern is thus strikingly remarkable between the somatic cell of the dog and the stem-cell of the venereal tumor studied here.
    It is interesting to note that the chromosomes of the present tumor show a considerable difference, either in number or in morphology, from those of the dog venereal tumor of similar nature which was studied by Watanabe and Azuma (1956) in Nagasaki.
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  • Taizo NISIOKA
    1958 Volume 33 Issue 2 Pages 65-68
    Published: 1958
    Released on J-STAGE: November 30, 2007
    JOURNAL FREE ACCESS
    1) The karyotypes of three species of Sonchus, one species Hieracium and one species of Prenanthes are reported.
    2) The chromosome numbers of Hieracium umbellatum var. japonicum and Prenanthes Tanakae are here reported for the first time.
    3) Sonchus oleraceus seems to be an amphidiploid considering from the karyotypical stand point. But the Stebbins' opinion that Sonchus oleraceus may be an amphidiploid containing eighteen chromosomes of S. asper plus the fourteen chromosomes of S. Tenerrimus can not be confirmed from this karyotype analysis.
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