Cataractous mice (Cts/Cts homozygotes) were reciprocally crossed with 4 inbred strains of mice. In F1, expressivity of the gene fluctuated depending upon the background genes. Expressivity of the gene in F1 was different from that in their F2, reflecting the heterogeneous genetic constitution of the latter. The Cts gene possessed complete penetrance, as might be expected of an autosomal semidominant gene. The initial sign of cataract formation was found at prenatal day 15 in the lens fibers near the anterior pole area of Cts/Cts homozygotes.
The mechanism of the enhancing effect of nucleosides on catabolite repression of β-galactosidase synthesis by glucose or glycerol was studied. For this purpose, mutants of Escherichia coli strain 3000 deficient in the catabolic enzymes, thymidine phosphorylase, purine nucleoside phosphorylase, and phosphodeoxyribomutase were isolated. Strain W3110-215 (λ-, thy-, deoC-), a derivative of strain W3110 (λ-, prototroph), deficient in deoxyriboaldolase was also used. Catabolite repression of β-galactosidase synthesis by glucose was enhanced by adenosine but not by thymidine in a mutant deficient in thymidine phosphorylase, by thymidine but not adenosine in a mutant deficient in purine nucleoside phosphorylase, and by both thymidine and adenosine in a mutant deficient in phosphodeoxyribomutase. In strain W3110-215, adenosine increased catabolite repression of β-galactosidase by glycerol, whereas thymidine inhibited the synthesis completely after a lag of about 20 min in the presence or absence of glycerol, probably due to accumulation of some growth inhibitory substance, such as deoxyribose 5-phosphate (or its derivative(s)) formed from thymidine. These results suggest that nucleosides must be catabolized further than deoxyribose 1-phosphate or ribose 1-phosphate to exert an enhancing effect on repression of β-galactosidase by glucose or glycerol.
Studies on development in vitro of excised ovaries in the crosses of various cultivars in B. campestris×B. oleracea were carried out. Ovaries excised 4 days after pollination were cultured in vitro. The medium was composed of White's medium (1963) supplemented with 300mg/l of casein hydrolysate, 50g/l of sucrose and 8g/l of agar. Many seeds and well developed naked-embryos protruded from undeveloped seed coat were obtained in the capsules examined. These embryos were further cultured on the medium and many interspecific hybrid plants were obtained in various ultivars of B. campestris×B. oleracea. Production rate of hybrid plants was different in different subspecies of B. campestris used as female plants. Culture in vitro of excised ovaries on the medium with casein hydrolysate is useful as a new technique for production of interspecific hybrid plants in B. camestris× B. oleracea.
The frequency patterns of the different kinds of dumpy mutations induced by X-rays (1, 500 and 3, 000R) in the successive stages of oocyte development were investigated by transferring the inseminated females daily to fresh vials for 12 days. Under this transferring procedure, the first egg-laying period represents oocytes irradiated when they are at stage 14, and the subsequent ones represent progressively earlier stages of oocyte development at the time of irradiation. The results obtained indicate that (1) the overall yield of complete dumpy mutations recovered in the first six day egg-laying periods (1st-6th day) are relatively higher than that in the subsequent six day periods (7th-12th day), showing a response pattern with a higher mutation frequency in the early egg-laying periods and a lower frequency in the late egg-laying periods; (2) the frequency patterns for the exceptions of the ol and lv types and those of ov and olv types through the ampling periods are practically similar to those observed in the total dumpy mutations; (3) a somewhat peculiar frequency pattern, which seems to be variable by dose, is found in the yield of the o and v exceptions. At the exposure level of 1, 500R, no definite difference in response pattern for these exceptions is found, though a response pattern which is practically similar to that observed in the total dumpy mutations is found at the exposure level of 3, 000R. The foregoing findings seem to indicate that the different kinds of dumpy exceptions are affected at various degrees by the difference in the cell stages of oocyte. This may possibly suggest that these exceptions are different from each other in the nature of their mutations, that is to say, whether they are associated with chromosome breakage events or not.
Both cadmium and furylfuramide were highly toxic at every develompental stage of Drosophila, resulting in prolongation of the developmental time, lowering of the viability and decreasing of the egg production. However, these chemicals give no mutagenic effects either in the sex-linked or in the second chromosome lethal test.
In order to identify specific monosomics and nullisomics, twenty one monosomics and four nullisomics of hexaploid oats were investigated for their peroxidase isozymes in flag leaves by gel electrofocusing method. Five monosomics (i. e., Mk 3, 4, 9, 22 and 24) and four nullisomics (i. e., N9, 11, 24 and 26) of Kanota oats could be distinguished from the disomic line by peroxidase isozymes. A larger number of the bands decreased their activities in all the nullisomics examined. Although the peroxidase isozymic systems of hexaploid oats are thought to be very complex, analysis of peroxidase isozymes is useful for identification of some monosomics and nullisomics in hexaploid oats.
Two dwarf strains of rice, Tan-ginbozu and Waito-C, and their cross with Norin 29 (tall) were investigated with regard to the inheritance of the plant height and the activity of GAs. Tan-ginbozu gene is responsible for the control of overall GA production. Waito-C has another recessive gene at an independent locus which blocks the production of particular GAs.
Photo-preferences of the sibling species, Drosophila simulans and D. melanogaster, were studied using an apparatus and population cage having a gradient of light intensities. D. simulans preferred to stay and to lay eggs at light places whereas D. melanogaster did not show such a strong light preference. Selections of eggs in the light gradient cages made it possible to segregate a mixed species population into different species populations; selection for photo-positive flies soon eliminated D. melanogaster and slection for photo-negative or photo-neutral flies finally eliminated D. simulans. The difference of the photo-preference seems to be a cause of coexistence of the sibling species in nature.