The activity and the processivity in DNA relaxation of DNA topoisomerase II, isolated from cauliflower inflorescence, were examined with various ratios of KCl and MgCl2 concentrations in the reaction medium. The optimum concentrations for the relaxation were found to be 60mM for KCl and 5mM for MgCl2 in the same reaction mixture regarding the other elements. The reaction proceeds in a processive manner at low salt concentration, and in a distributive manner at high concentration, in which MgCl2 exhibits higher efficiency (five-fold) than KCl.
To investigate the distance between Nd-s and Fib-L on the 14th chromosome of Bombyx mori, a three-point test cross involving U, Nd-s, and Fib-L was carried out. The crossover frequency between U and Fib-L or U and Nd-s was 24.6%. Crossingover between Fib-L and Nd-s was not observed. These results indicate that Fib-L is closely linked with Nd-s. In the fibroin slightly secreted into the lumen of the posterior silk gland of the Nd-s mutant silkworm, fibroin L-chain was not detectable. A possibility that the Nd-s phenotype is caused by a mutation in the L-chain gene, is discussed.
Nicotiana glauca chloroplasts can be distinguished from N. langsdorffii chloroplasts by a difference in size of the Bam HI restriction endonuclease fragment of chloroplast DNA (ctDNA), and by a difference in the isoelectric focusing pattern of the large subunit of Fraction I proteins. Chloroplast DNA and Fraction I protein were isolated from parasexual hybrid calli derived from cell f usions between N. glauca and N. langsdorffii. Results obtained from 16 calli showed that the expression of the N. glauca type large subunit was correlated with presence of N. glauca ctDNA, N. langsdorffii large subunit with N. langsdorffii ctDNA. Whenever two kinds of ctDNA were present in a callus, both types of large subunit were expressed. Although the Bam HI fragment is distant from the gene for the large subunit, no evidence was obtained for recombination between these two ctDNA markers.
The ATP pool and the cellular ATP level of a temperature-sensitive dnaK mutant were determined from the amount of total ATP measured by a modified ATP assay method, the number of viable cells, and dry cell weight. When the mutant cells at the mid-logarithmic phase were exposed to nonpermissive temperature, the initial levels of the ATP pool (5.07nmoles per mg dry cells) and cellular ATP (3.62nmoles per viable cell) remained nearly unchanged for over 3h. In the parental cells, however, both the ATP pool and the cellular ATP level decreased to one-third the initial levels. After 3h at permissive temperature, the ATP pool remained nearly unchanged but the cellular ATP level decreased to about 30 percent of the initial levels in both the mutant and parental strains. Our ATP assay method is quick and more easier; it is also reliable, because it provided values of the ATP pool that agree well with the values reported elsewhere.
Interactions among three sex-specific lethals, da, Sxlf#1 and mle(3)132 of Drosophila melanogaster were studied as to the effects on viability and sex transformation. Six crosses involving these mutants were made. The results showed that mle(3)132 interacts with the da-Sxl system both maternally and zygotically. These two effects are opposite in action. Maternal mle(3)132 enhances both lethal and sex transforming actions of the da-Sxl system. Zygotic mle(3)132, on the contrary, suppresses the lethal action. Roles of these three sex-specific lethals are discussed in relation to sex determination and dosage compensation.
Cytoplasmic relationship between 37 tuberous Solanum accessions and hybrids and two Lycopersicon species was investigated by restriction fragment pattern analysis of chloroplast DNA using eight endonucleases. Variations found in their chloroplast DNAs were subjected to mutation analysis, from which a phylogenetic tree was constructed as shown in Fig. 4. The 30 species studied are classified into four groups from their chloroplast DNA similarities: (1) South American species and Mexican polyploid species, (2) Mexican diploid species, (3) S. etuberosum, and (4) S. lycopersicoides and Lycopersicon species. These groups correspond well to the groups established from crossability by Hawkes (1978). Cytoplasmic differences between 22 species in the first group are so small that these species seem to be of recent origin. Mexican diploid species in the second group greatly differ from those in the first group, and also from each other. S. etuberosum differs from all others by, at least, 21 mutational changes. S. lycopersicoides is rather closely related to the Lycopersicon species, and is different from other Solanum species by, at least, 21 mutational changes. Cytoplasms of all cultivated species except common potato, S. tuberosum ssp. tuberosum have originated monophyletically from S. stenotomum. The cytoplasm of common potato is revealed to have derived from Chilean tuberosum as pointed out by some workers, but the cytoplasm donor to Chilean tuberosum remains unidentified.
Male flies of Drosophila auraria have about 14 bristles on the 6th sternite, while those of D. biauraria have generally none. Backcross experiments were made by using mutant markers of D. auraria chromosome. It was found that both the X and A-chromosomes were obviously responsible for the bristle manifestation. A chromosome assay was made by using a mutant strain of D. auraria being homozygous for y, cn and cu. The A-chromosome had a major effect which manifested 8.6 bristles on an average and the X had a moderate one being conformable to 4.1. The effect of the B-chromosome was a little, corresponding to 1.1 at the most. Interactions between the effects of chromosomes were negligibly small in all combinations.
A reciprocal chromosomal translocation strain, T (I; II) KH 5-9, was obtained by spontaneous chromosomal rearrangements. In strains heterozygous for KH 5-9, 50-60% of the ascospores are aborted. The ascus frequencies (black: white) were 27% 8:0, 18% 6:2, 27% 4:4, 9% 2:6 and 14% 0:8. In homozygous strains 0 to 10% of the ascospores were aborted. The strain harbored in the left arm of LG I a chromosomal break point between leu-3 and un-3 very close to ser-3. The resulting left arm of LG I has been translocated to the right arm of LG II distal to un-20 at very near position to ace-1. The right arm of LG II has been translocated to the left arm of LG I. The direction of chromosomal attachment of LG IL to LG IIR was from arg-12, un-20 (LG IIR), break point, leu-3 and un-5 (LG IL). Strain T (I; II) KH 5-9 was inseparable from morphological mutations designated eas-2 (easily wettable-2) and brm (branched mycelia). Strain with brm was derived from T (I; II) KH 5-9 eas-2 and zygotes between them produced 0 to 10% of abortive ascospores. Strains with eas-2 form conidia readily soluble to water and strains with brm form aconidial mycelia with defective cell wall. Forced heterocaryon between them formed wild type hydrophobic conidia. In the zygotes between them, brm and eas-2 behaved closely linked to mating type and un-3. From these results KH 5-9 was assumed to harbor one or closely linked two mutations in the regulator for eas-2 and brm.
We have cloned and characterized several P transposable elements from P and Q strains extracted from natural populations of Drosophila melanogaster in Japan. Structures of these clones were investigated by the techniques of blot hybridization, restriction mapping, and observation of heteroduplex by electron microscope. No intact P element such as pπ 25.1 was found among 11 clones from a P strain and 10 clones from Q-strains. A typical Q-strain (WY-113) judging from the results of genetical crosses did not carry any DNA segment homologous to pπ 25.1, indicating the complex nature of Q-strains.
An extremely large detrimental to lethal load ratio (D/L ratio) of homozygous viability was detected in the Osaka natural population of Drosophilamelanogaster in 1979. Mutations were accumulated on 79 second chromosome lines that originated from one of the Osaka isogenic second chromosome lines. After five generations the genetic load and ADH specific activity were measured. The results suggest that a putative transposon which is tentatively called "MY factor" induced an extremely high frequency of mutations most probably in non-coding regions, and that some of these mutations modify the ADH specific activity.