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Volume 38 (1963 - 196･･･
- Issue 5-6 Pages 311-
- Issue 4 Pages 237-
- Issue 3 Pages 159-
- Issue 2 Pages 89-
- Issue 1 Pages 1-
Volume 38, Issue 4
Displaying 1-9 of 9 articles from this issue
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Shin TAKEHISA1964 Volume 38 Issue 4 Pages 237-243
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESS1. The karyotype of Petunia hybrida was re-investigated and was determined as follows. K(2n)=14=2csAsm1(n) +2Am2+2Bst+2Cm1+2Csm2+2Dsm1+2Dm2.
2. The present study has revealed the differential chromosome condensation to take place from late prophase to metaphase in somatic mitosis. And the differential chromosome condensation probably has its relationship to heterochromatin.View full abstractDownload PDF (1388K) -
Yoshiaki KITANI1964 Volume 38 Issue 4 Pages 244-256
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSIn order to bridge the genetical requirements to the cytological understandings on the behaviours of somatic chromosomes, followings were subjected in the present works: a) whether or not somatic chromosomes are under the control of some tying force during the mitotic cycle, b) whether or not homologous chromosomes become intimate sometime in mitosis, and c) whether the concept of half-chromatid structure is applicable on early anaphase chromatids under the light microscope.
Root-tips of Crepis capillaris and young endopserm tissues of Aegilops squarrosa were mainly used.
Chromosomes were found orientated at their kinetochore regions throughout prophase, and homologous chromosomes were found in “side-by-side” arrangement throughout the cell generations. Association of homologous chromosomes was found in late telophase of mitosis in Crepis capillaris. The double structure of mitotic anaphase chromatids was clearly observed in Crepis.
From above observations, little “free wandering” of individual chromosomes throughout mitotic cycle, and the presence of the intimate period of homologous chromosomes prior to the DNA replication were considered to be reasonable. The possibility of the occurrence of recombinations and aberrant gene reproductions through mitosis were simultaneously discussed.View full abstractDownload PDF (3186K) -
Yuh H. NAKANISHI, Hatao KATO, Tamiko IWASAKI1964 Volume 38 Issue 4 Pages 257-260
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSDownload PDF (800K) -
VI. Isolation and Chracterization of Spontaneous Variants Resistant to CadmiumHakobu NAKAMURA1964 Volume 38 Issue 4 Pages 261-269
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSBy using the method of sib selection followed by the replica-plating, a cadmium resistant clone (r1) was isolated from a sensitive strain (Par), and a clone of a higher resistance level (r2) from r1. Thus, r1 and r2 were shown to be of pre-adaptive nature. However, the strain of still higher resistance, obtainable by culturing in the presence of cadmium, has not been isolated by the indirect selection.
The mutation rate from Par to r1 and that from r1 to r2 were 6.3×10-9 and 4.0× 10-8 per cell per budding cycle, respectively. Growth of r1 was slower than Par, and r2 than r1, in their mixed cultures.
r1 was more resistant to copper, cobalt and nickel than Par, but r2 was less so than r1 except for nickel.View full abstractDownload PDF (688K) -
Koichiro TSUNEWAKI1964 Volume 38 Issue 4 Pages 270-281
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSFrequencies of monosomics in progenies from self- or cross-pollinated monosomics of a common wheat variety, Chinese Spring, were estimated from the data accumulated during nine years in U. S. A., Canada and Japan. Analysis has been made of several factors. which might be concerned with the frequency of monosomics. The results are summarized as follows:
1. Contrary to the expectation, over-all frequency of monosomics in self-pollinated progenies was lower than in cross-pollinated ones. This tendency was most pronounced in monosomics of homoeologous group 1. Poorer viability of monosomic embryos of pure monosomic lines than that of hybrids was assumed to be the cause.
2. In general, frequencies of monosomics observed in America and Japan were the same. However, mono-5A showed an extremely high transmission rate of monosomic condition in Japan.
3. The monosomic frequency significantly differed among 21 monosomic lines. Mono-6B showed the lowest frequency (57.3%) and mono-5A the highest (81.9%). Frequencies of the other monosomics were intermediate.
4. Monosomics belonging to the same homoeologous group showed in general similar frequencies. Homoeologous group 1 (79.5% except mono-1B), 6 (77.8% except mono-6B) and 3 (76.3%) are characterized by high and group 2 (67.1%) by low transmission rate. The other three groups had an intermediate frequency.
5. Three monosomics showed a deviation in the frequency from those of the two other monosomics belonging to the same homoeologous group. The frequencies of mono-1B and -6B were low and that of mono-5A was high. Low frequencies of the former two are probably correlated to the localization of the nucleolus-organizing region on chromosomes 1B and 6B. High frequency of mono-5A might be related to the speltoid character, for which chromosome 5A is responsible.
6. High correlation was found between the frequency of monosomics and both seed-setting percentage and germination rate. No correlation was detected between the former and either chromosome length, frequency of pollen tetrads with micronuclei or frequency of chromosome-deficient male gametes. This result indicates that the transmission rate of monosomic condition is mainly determined by the viability of monosomic embryos.View full abstractDownload PDF (1054K) -
Terumi MUKAI, Isao YOSHIKAWA1964 Volume 38 Issue 4 Pages 282-287
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSHeterozygous effects of mutations induced by low doses of X-irradiation on viability were tested both in otherwise homozygous genetic background and in heterozygous genetic background in Drosophila melanogaster. On the basis of counting approximately 1.46 million flies, it was found that radiation-induced mutations which occurred in homozygous genetic background were heterozygously beneficial to their carriers, while those induced in hybrids between individuals originated from two unrelated populations were slightly detrimental to their carriers.View full abstractDownload PDF (560K) -
Y. MATSUDAIRA, T. ITO, T. YAMASAKI, S. ISHIZAKA, M. DOMON1964 Volume 38 Issue 4 Pages 288-289
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSDownload PDF (189K) -
Sumio MINAMORI, Yoshinori SAITO1964 Volume 38 Issue 4 Pages 290-304
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSFrequency of the second chromosomes bearing lethal gene (or genes) in natural populations was examined in five stations, in summer and autumn seasons and in successive years in Hiroshima Prefecture. The combined frequencies of lethal and semilethal chromosomes varied with the stations, seasons or years from 2.2 per cent to 20.7 per cent. The allelic rates within a population ranged from zero to 60 per cent. These results suggest that these populations were small in size. From the results of allelic rates, the narrowest territory of a breeding unit was estimated. The frequency of lethal chromosomes was revealed to be increased by 2.53 per cent and that of semilethal ones by 0.99 per cent from summer to autumn, and about seven generations may elapse in natural populations during this period. The combined increment of lethal and semilethal chromosomes was statistically significant. The allelic rate was observed to be decreased by 2.26 per cent during the two seasons. In spite of such an accumulation of lethal genes or decrease of allelic rate in the breeding season, any remarkable changes in the frequency or rate were not observed in the same season of successive years. Therefore, the seasonal changes in lethal frequency and the allelic rate seem to be repeated from year to year with the same fluctuation.
Based on these results, the breeding mode of natural populations of D. melanogaster distributed in Hiroshima area was discussed.View full abstractDownload PDF (1278K) -
Kenji MATSUDA1964 Volume 38 Issue 4 Pages 305-309
Published: 1964
Released on J-STAGE: May 21, 2007
JOURNAL FREE ACCESSCytological effects of 5-bromouracil were observed in germ cells of Podisma sapporense. Most frequent chromosomal abnormalities were chromatid-breaks and erosion. Cells showing those aberrations were observed rather frequently in, and particularly limited to, the division of the secondary spermatocytes 20 to 60 minutes after chemical treatments. The position of breaks appeared rather constantly in the same chromosome and tended to localize on a point one-fourth of the chromosome adjacent to the centromere. The chromosomes with breaks divided in normal manner at anaphase. The rate of division tended to decrease in affected material for a long period of time.View full abstractDownload PDF (669K)
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