The Japanese Journal of Genetics 

About: The Japanese Journal of Genetics is an academic journal. The journal publishes majorly in the area(s): Population & Ploidy. It has an ISSN identifier of 0021-504X. It is also open access. Over the lifetime, 2298 publications have been published receiving 25698 citations.

Origin of the genic diversity of cultivated rice (Oryza spp.): study of the polymorphism scored at 40 isozyme loci

Abstract: An electrophoretic survey of up to forty presumed isozyme loci was carried out in Asian and African cultivated rice (O. sativa and O. glaberrima) and in weedy and wild forms of African O. breviligulata on a total of 1, 948 strains. Hidden variability was checked by a test of heat stability at thirty isozyme loci in the same species.The mean gene diversity index ("heterozygosity") was high (0.23) in O. Sativa, medium (0.14) in wild O. breviligulata and low (0.06 and 0.03) in weedy O. breviligulata and O. glaberrima.In contrast, a maximum of seven alleles at a single locus could be distinguished in wild O. breviligulata while only three at the most were found in O. sativa and two in O. glaberrima and the weedy forms of O. breviligulata.Calculations of genetic distances showed that the cultivated, wild and weedy African species formed a genetic group distinct from O. sativa. Multivariate analysis of the data on an individual strain basis confirmed this fact and showed in turn that most varieties of O, sativa tended to cluster in two groups which correspond to the so-called Indica and Japonica subspecies. There was however a continuous array of intermediates between the two groups.Multivariate analysis also showed that the endemic African strains with the most genetic affinity to O. sativa were certain strains of the weedy form of O. breviligulata.Analysis of F1 pollen sterility among 115 strains of O, sativa permitted the extraction of one small Indica and one small Japonica group of strains characterized by a high pollen sterility relationship but most strains were intermediate.Each group had little gene diversity, with more than 80% of the loci fixed for one allele. Their isozyme patterns were remarkably complementary in that most of the various gametic associations of alleles found in the numerous intermediate strains could be explained by hybridization between varieties belonging to one and the other group. Consequently, these were assumed to represent the ancestral isozyme patterns of the Indica and Japonica subsp.Similar genetic distances, which point to a divergence time of one to a few millions years ago were found between O. glaberrima and the ancestral types of Indica and Japonica in the three combinations.Assuming the neutral theory of isozyme polymorphism, the data confirmed that O. glaberrima was domesticated from O. breviligulata independently of O, sativa. They also suggest that, at the origin of O. sativa, the Indica and the Japonica types were also domesticated independently. The large diversity of O. sativa would result: (i) primarily from introgressions that occurred between the ancestral cultivated types, together with the selection imposed by man, and (ii) secondarily, following the dispersion of cultivars, from the introgression of genes of wild rice in various areas. Some of the weedy forms of O. breviligulata could have originated from natural hybrids between the two cultivated species, O. sativa and O. glaberrima.

Genotype by Environment Interaction and Genetic Correlation of the same Trait under Different Environments

Abstract: The present paper is an attempt to compare the methods of estimating genetic correlations, one from the original variance and covariance analyses and the other from the two-way analysis of variance.By contrasting the expected mean squares in the latter in terms of variance and covariance in the former, the standard estimation formula of genetic correlation was expressed by means of variance components in the two-way analysis.

Modes of spontaneous chromosomal mutation and karyotype evolution in ants with reference to the minimum interaction hypothesis.

Abstract: Aspects of chromosomal mutation and karyotype evolution in ants are discussed with reference to recently accumulated karyological data, and to detailed karyotype analyses of several species or species complexes with low chromosome number and unusual chromosomal mutations (the complexes of Myrmecia pilosula (Smith) (n=1, 5 or 9 to 16); M. piliventris Smith (n=2, 3-4, 17 or 32), and Ponera scabra Wheeler (n=3 or 4, 2n=7 or 8)). Translocations and Robertsonian polymorphisms are confirmed to be non-randomly distributed among ants -the former are found at high frequencies in species with low chromosome numbers (n≤12), while the latter predominate in those with high numbers (n>12). This situation is consistent with the minimum interaction hypothesis of Imai et al. (1986), under which translocations are expected to occur most frequently in low-numbered karyotypes, and that the resulting genetic risks are minimized by increases in chromosome and/or arm numbers through centric fission and pericentric inversion. Centric fusion is considered to be a transient event in karyotype evolution, resulting from telomere instability in acrocentric chromosomes.

The neutral theory of molecular evolution: a review of recent evidence.

Abstract: In sharp contrast to the Darwinian theory of evolution by natural selection, the neutral theory claims that the overwhelming majority of evolutionary changes at the molecular level are caused by random fixation (due to random sampling drift in finite populations) of selectively neutral (i.e., selectively equivalent) mutants under continued inputs of mutations. The theory also asserts that most of the genetic variability within species at the molecular level (such as protein and DNA polymorphism) are selectively neutral or very nearly neutral and that they are maintained in the species by the balance between mutational input and random extinction. The neutral theory is based on simple assumptions, enabling us to develop mathematical theories based on population genetics to treat molecular evolution and variation in quantitative terms. The theory can be tested against actual observations. Neo-Darwinians continue to criticize the neutral theory, but evidence for it has accumulated over the last two decades. The recent outpouring of DNA sequence data has greatly strengthened the theory. In this paper, I review some recent observations that strongly support the neutral theory. They include such topics as pseudoglobin genes of the mouse, αA-crystallin genes of the blind mole rat, genes of influenza A virus and nuclear vs. mitochondrial genes of fruit flies. I also discuss such topics as the evolution of deviant coding systems in Mycoplasma, the origin of life and the unified understanding of molecular and phenotypic evolution. I conclude that since the origin of life on Earth, neutral evolutionary changes have predominated over Darwinian evolutionary changes, at least in number.

Restriction fragment length polymorphism (RFLP) analysis in wheat. II. Linkage maps of the RFLP sites in common wheat

Abstract: Sixty-six F2 plants from the cross, Triticum aestivum cv. Chinese Spring (abbrev. CS) x T. spelta var. duhamelianum (Spelta), exhibiting the greatest number of RFLPs among eight common wheats, were analyzed for their RFLP genotypes using genomic DNA clones of CS as probes. In total, 204 RFLP loci were identified and their linkage relationships established. By nulli-tetrasomic analyses, all linkage groups were assigned to one another of the 21 wheat chromosomes. In addition, the carrier chromosomes of 228 non-RFLP loci were identified. The linkage maps of these RFLP loci have a total size of 1800 cM and exceed those of the classical genes in both size and locus number. Twenty loci show distorted segregation, four of which are clustered on chromosome 4A and three on the 2D chromosome. The CS alleles on 4A exhibit preferential transmission, while those on 2D exhibit depressed transmission, compared with Spelta alleles. This suggests the influence of gametic factors in those regions. RFLP loci are much fewer in the D genome than in the A and B genomes, but the numbers of non-RFLP loci are nearly the same in these three genomes. This suggests that Spelta wheat originated from a hybridization between T. dicoccum (spelt emmer) and T. aestivum.