Idengaku zasshi最新文献

We analyzed the restriction fragment length polymorphisms in the spacer regions of ribosomal DNA (rDNA), using twelve restriction enzymes, to examine whether the Iriomote cat is related to the leopard cat (Felis bengalensis). A restriction map for each taxon was constructed and the major taxon-specific types of repeating unit (repetypes) were characterized on the basis of the arrangements of restriction sites. The Iriomote cat and the leopard cat share a common repetype but this repetype is different from that of the domestic cat (F. catus) with an estimated sequence divergence of 1.5% and from that of the ocelot (F. paradalis) with an estimated sequence divergence of 2.5%. These results indicate that, phylogenetically, the Iriomote cat is closely related to the leopard cat and that the ancestral population moved from the continent to Iriomote Island quite recently. The rDNA arrays of the leopard cat exhibit considerable intragenomic size-variation, which is thought to have emerged as a result of differences in numbers of repeated DNA segments, whereas the extent of such size-variation is much lower in the rDNA of the Iriomote cat. It appears that, even though migration of the Iriomote cat occurred relatively recently, the population has diverged to some extent from its continental counterpart, perhaps via fixation of preexistent intraspecific variations rather than by generation of new variations.

Restriction map polymorphism at two X linked foci, forked and vermilion of Drosophila melanogaster was studied in three natural populations. The estimates of nucleotide variation were theta = 0.003 and pi = 0.002 for the forked region and theta = 0.004 and pi = 0.002 for the vermilion region. Three insertions (> 500 bp) were observed at each locus. Typical of other regions of this species each of these large insertions was unique in the sample. Non-random association among polymorphisms was common at the vermilion locus, while the forked locus was not polymorphic enough to test linkage disequilibrium. The amounts of restriction site and size variation in the vermilion and forked were within the range observed for other loci of D. melanogaster.

In order to understand the evolutionary process of self-incompatibility, we must know the genetic variability of the self-incompatibility genes within and between populations. Statistical methods for estimating the effective number of alleles, expected heterozygosity and genetic distance from pollination experiments were developed, which can be applied to both gametophytic and sporophytic self-incompatibility systems. In these methods, bud-pollination, which is necessary for obtaining homozygotes, is not required. Since bud-pollination, which is time-consuming, is not required in the present methods, they might be useful.

Morphometric variability was studied in six domestic Venezuelan populations of the blood-sucking bug Rhodnius prolixus Stal 1897 (Reduviidae, Triatominae) and in a sylvatic population identified as R. robustus Larrousse 1927. Evidence is here provided by both uni- and multifactorial analyses of extensive variation of morphological traits between the R. prolixus populations studied. Regardless the geographic or climatic environmental factor tested, none can be retained in a selective model accounting for the morphological variability observed. Moreover, the results failed to support any correlation between the morphological Mahalanobis' distances and geographical distances. The genetic relationships between these populations inferred from the present data, are more consistent with some demic structure, resulting from random genetic drift by founder effects, than with any alternative population genetic model. It is noteworthy that the range of variation of these morphological traits in R. prolixus includes the putative R. robustus population. Therefore, the species-specific status of R. robustus, at the very least the local Trujillo population studied, is questioned. In addition, a preliminary multifactorial analysis bearing on the three other Rhodnius relatives, R. pictipes Stal 1872, R. nasutus Stal 1859 and R. neglectus Lent 1954, confirmed the marked morphological differentiation of R. pictipes from all other species and showed a clear morphological differentiation of R. nasutus and R. neglectus both from one another and from R. prolixus.

A comparative study was done on the enzymological features of alpha-amylase among six sibling species belonging to the Drosophila melanogaster species subgroup. The pH optima were 7.6 for D. melanogaster, D. mauritiana and D. simulans and 7.4 for D. erecta, D. teissieri and D. yakuba. The temperature optima were commonly 37 C in all species studied. However, there are two types of temperature dependence; a strict one as observed in D. melanogaster, D. mauritiana and D. simulans, and a flat one as observed in D. erecta, D. teissieri and D. yakuba. These separations are consistent with the general phylogeny within this species subgroup. The substrate dependence was almost the same in all the species studied. The Vmax and Km were also estimated for each species. We found clear differences in the enzymological features between the species. Thus these differences might reflect an adaptation of the amylase enzyme system to speciation in this species subgroup.

To analyze the region that determines the specificity of binding of the Tn3 transposase to the terminal inverted repeat sequences (IR), we first determined the nucleotide sequence of a Tn3-family transposon, gamma delta, which is supposed to encode a transposase similar to that of Tn3. gamma delta was 5981 bp in length and contained three coding frames: Two were the genes, tnpA and tnpR, encoding transposase (1002 amino acids) and resolvase/repressor (183 amino acids), respectively, and the third, named tnpX, encoding a protein (698 amino acids) of unknown function but containing two NTP-binding motifs. Utilizing the tnpA sequence, we then constructed a series of Tn3-gamma delta hybrid genes encoding chimeric proteins in the N-terminal segments of the transposases (amino acid position 1 to 242 of Tn3 or 1' to 243' of gamma delta), which has been previously shown to be responsible for specific binding of transposase to IR sequences in Tn3. Examination of their DNA-binding activities revealed that the subsegment of the N-terminus from amino acid position 1 to 109 determines the specificity of binding to the IR sequences. The third coding frame found in gamma delta, tnpX, is located downstream of tnpR and is expressed from the tnpR promoter in the absence of the tnpR gene product, resolvase/repressor, to produce a protein that inhibits the growth of the host cells. Possible roles of this protein are discussed.

Fragile X syndrome is the most common familial form of mental retardation and known to be associated with the fragile site at Xq27.3 (FRAXA). The syndrome has recently been characterized by a unique genetic mechanism which involves dynamic mutation due to a heritable unstable DNA sequence, p(CCG)n repeat, in the FRAXA locus. We were asked to make a genetic diagnosis on the case of a normal male who has two brothers and a maternal uncle with mental retardation. We performed the pedigree analysis of the fragile X syndrome using both cytogenetic and molecular techniques. The affected two brothers and the uncle showed cytogenetic expression of the fra (X)(q27.3) and carried hypermethylated full mutation in the FRAXA locus. The phenotypically normal mother also exhibited fragile X expression and was found to be a carrier of premutation. Via female transmission, the premutation converted to full mutation and exhibited somatic heterogeneity and hypermethylation. However, both cytogenetic and molecular data did not show any evidence of fragile X mutation in the normal male client and, thus, excluded the possibility of his being a carrier.

Cytological investigations of salivary gland polytene chromosomes of the Drosophila kikkawai complex in Thailand have revealed an interesting pattern of species divergence. Drosophila bocki, D. leontia and D. kikkawai share chromosome arrangement 3LB. However, additional gene arrangements of 3LA and 3LC have been observed in D. kikkawai and D. leontia, respectively, while D. bocki remains polymorphic for inversion 3LB. Chromosomal evidence seems to suggest that D. bocki is similar to a common ancestor of the D. kikkawai complex.

Drosophila albomicans is a species widely distributed but mainly in Southeast Asia. In its traditional distribution, there are substantial genetic differentiations among three geographic areas, Southeast Asian continent, Taiwan and Nansei islands. In the last decade, however, this species has invaded the Japanese mainland and is now spreading its distribution area to western Japan. In this study, variations of chromosomal arrangements, allozymes and sex ratio in F2 hybrids with D. nasuta were examined to identify the origins of the newly colonizing population. The results strongly suggest that the origins of Japanese mainland population can be found in Taiwan.

Partial DNA regions encoding a major part of translation elongation factor 2 (EF-2) from a mitochondria-lacking protozoan, Entamoeba histolytica, were amplified by polymerase chain reaction and their primary structures were analyzed. The deduced amino acid sequence was aligned with other eukaryotic and archaebacterial EF-2's, and the phylogenetic relationships among eukaryotes were inferred by the maximum likelihood (ML) method. The ML analyses using four different stochastic models of amino acid substitutions consistently suggest that among eukaryotic species being analyzed, E. histolytica is likely to have diverged from other higher eukaryotes on the early phase of eukaryotic evolution.