Chromosome numbers in callus cell cultures derived from nulli-5B tetra-5D, ditelo-5AL, -5BL and -5DL of Triticum aestivum cv. Chinese Spring were found to be more variable than those of the control, especially in ditelo-5AL. The number of telocentric chromosomes varied from one to eight but showed no significant tendency to increase or decrease.
Crown gall tumors of the pea were studied karyologically during different periods of tumor development. Diploid and tetraploid cells were observed at nearly equal frequency during almost all collection periods, and both showed normal karyotype 15 days and 80 days after inoculation. This suggests that anomalies of karyotype are not the cause or result of further development of the tumor. Octoploid cells were also seen at almost every collection period, and even 16-ploid cells appeared occasionally. Mitotic frequency was found to persist at about 2% up to 100 days after inoculation. This suggests that cell division at a constant rate continues unlimitedly unless the physiological activity of the host plant declines.
The presence of higher polyguanylate (poly G) synthesizing activity was observed in soluble chromatin from cauliflower infloresence under the present assay conditions. The effects of pH, ionic strength of some inhibitorial reagents for poly (G) synthesizing activity was found to be different from that of polyadenylate (poly A) synthesizing activity, and also from the these enzyme activities in purified RNA polymerase preparation.
During the early stage of germination of barley seeds the nuclear chromatin, which was diffused fibrously in the first-leaf and root meristem cells, incorporated tritiated thymidine into them. These tritium-labeled nuclei increased significantly after the treatments of gamma rays and 4-nitro-quinoline 1-oxide (4NQO). With post-treatment of 1mM EDTA, radiation-induced incorporation of tritiated thymidine into the diffuse nuclei of irradiated seeds was inhibited. The results obtained suggest that unscheduled DNA synthesis occurs in accordance with or due to chromatin diffusion in barley cells after gamma-ray irradiation and treatment with 4NQO.
Acriflavine sensitive mutants were isolated from a wild type (acriflavine-resistant) strain of Escherichia coli K-12 and characterized. These mutants form giant colonies on a broth agar medium, unlike another mutant N43 (genotype acrA1) which has been studied. The mutations, both forward and backward, with regard to the colonial size always accompany changes in response to acriflavine, suggesting pleiotropy of gene. The giant colony-forming mutants were not only higher in the rate of exponential growth but also larger in cell size than their parent strains. The mutations fall in the acrA cistron as in mutant N43.
Wide variation of chromosome pairing configurations was observed at metaphase I proper in each F1 hybrid of A. strigosa (2n=14), A. barbata (2n=28), A. sativa (2n=42), A. fatua (2n=42) and A. sterilis (2n=42) crossed with A. longiglumis (2n=14) as given in Tables 1-5. Inspection of the data suggests an occurrence of a maximum pairing configuration of two associations of 6, and 8 chromosomes in A. longiglumis (AlAl, genome formula)× A. strigosa (AsAs) as well as two associations of 10 chromosomes and one univalent in A. barbata (AsAsBrBr)×A. longiglumis (AlAl). The chromosome associations can be formed as the result of the structural differentiation of the longiglumis genome, probably characterized by two single and three reciprocal translocations. It is also sure that the second genome (Br) of A. barbata (AsAsBrBr) is partially homologous with both of the As and Al genomes. Their homology relationships are illustrated in the scheme showing structural differentiation of chromosomes (Fig. 1). It is largely similar to that proposed by Holden (1966) although much modified. In the hybrids between A. longiglumis (AlAl) and hexaploids (general genome formula is AhAhChChDhDh) the chromosome behavior can be understood by assuming intergenomic chromosome pairing of Al-7-Ah-3-4-ChDh (Ch-3-4-Dh). It is very similar to As-7-Ah-4-ChDh (Ch-2-Dh) expected from the data observed by Kihara and Nishiyama (1932) in hexaploids×A. strigosa. Thus the evidence supports the view that several different genomes were derived from a common ancestral genome in the course of evolution of the genus Avena.
DNA of molecular weight of about 2×107 was extracted from red peppers. When seeds of T cultivar (upup, fafa, YY, C1C1) were treated with DNA from K cultivar (UpUp, FaFa, yy, c1c1), a variant was obtained which shows a dominant character, non-fasciculate (Fa-), of the DNA donor, but maintains another recessive trait, erect (upup). Another variant was obtained in which two Mendelian traits changed to those of the DNA donor (up→Up, fa→Fa). The changes were exactly the same as those induced by ordinary grafting, suggesting that the mechanism of hereditary changes obtained by grafting could be induced by DNA derived from the stock.
Analyzing the patterns of H-segments revealed in the cold treated chromosomes, Trillium×yezoense Tatewaki hyb. (2n=15, K1SU) was reconfirmed to be the natural hybrid between T. kamtschaticum Pall. (2n=10, K1K1) and T. apetalon Makino (2n=20, SSUU). Chromosomal polymorphism of the two parental species made the hybrid plants naturally chromosomally polymorphic. In reality, three hybrid plants from a single locality were different from one another in their chromosome constitutions. Pattern of H-segments of the chromosome complement of T.×miyabeanum Tatewaki hyb. (2n=20, K2TSU) was composite one of those of T. apetalon and T. tschonoskii Maxim. (2n=20, K2K2TT). All the ten hybrid plants ananlyzed were different from one another in their chromosome constitutions.