Using two strains of D. ananassae, male recombination and Minute mutation frequencies were assayed with regard to the age of the male parent. One of the strains, L8, was characterized by a progressive decrease in male recombination with increasing age of the male parent, while the other strain, E22, exhibited no such changes throughout seven two-day broods. The pattern of recombination frequency in chromosome 2 was parallel to that in chromosome 3 in each strain. It was concluded that the factors responsible for changes in male recombination with male age affect both chromosomes 2 and 3 in common. In contrast, the two strains were similar in their pattern of frequency changes in Minute mutations with increasing male age, with a peak in the 4th brood. Genetic systems regulating male crossing-over and Minute mutations are discussed.
Genetic elements controlling male recombination were detected in the autosomes of the two wild strains, L8 and TNG, and a marker stock, b Arc se; bri ru, of Drosophila ananassae. In the L8 strain, a dominant enhancer, En(2)-cm, which acts on both chromosomes 2 and 3 in unison, is located between the b and Arc loci in the left arm of chromosome 2. In addition, a reducer, Ra, of the En(2)-cm is located in the right arm of chromosome 3 of this strain. The action of the reducer is expressed as progressive decrease in recombination frequency with increasing age of male parent. No such single major enhancer was present in the TNG strain. However, each of the three arms, 2L, 2R, and 3R, was found to carry genetic elements which cause male recombination. A suppressor, Su(2)-bs, which almost completely suppresses male recombination in males carrying En(2)-cm, was found in the left arm of chromosome 2, between the bw and Arc loci, of the b Arc se; bri ru stock. This suppressor has no effect on the polygenic enhancers of the TNG strain.
Cytogenetic observations conducted on 9 strains belonging to the leucosphyrus group (Colless 1956) and their hybrids have revealed the evolutionary facts of the process of divergence among them. Previous paper (Kanda et al 1981b) reported some results of hybridization among them. Three strains- Bangkok (BKK), Kanchanaburi (KCH), and Chantaburi (CTB)-from Thailand can be designated as a subspecies Anopheles balabaceesis dirus, with a small degree of divergence between the latter two strains. Two strains IMR and Kampong Sungai Ular (KSU) from Peninsular Malaysia can similarly be classified as a subspecies Anopheles balabacensis balabacensis B, while the strain Kota Belud (KTD) from Sabah with different genetic characters can be designated as a subspecies Anopheles balabacensis A. These 3 subspecies are included in the balabacensis complex. The two strains from Sarawak (SWK and SWN) were confirmed as a separate species designated as Anopheles leucosphyrus sensu stricto (Kanda et al 1981a) but with homosequential chromosome banding patterns of the leucosphyrus group (Reid 1968). A strain from Taiwan (TSG) is more closely related to CTB than KCH. There may exist some other closely related geographical populations. However, the designation of TSG as a valid species Anopheles takasagoensis distinct from balabacensis can not be confirmed due to insufficient data. Interstrain floating rearrangements of banding patterns were observed in the XR arm of KCH, IMR and CTB strain as well as in the hybrids. Additional descriptions of 2 chromosomal polymorphisms within the species group are given.
Six cell suspension lines (Kp9, Kp10, Kp20, Kp42, Tp1 and Tp4) established from pollen calli of two Paeonia cultivars have been studied with special reference to their growth characteristics and chromosomal behavior. They reached stationary phase after about 14 days of subculture showing about a 6- to 10-fold increase in packed cell volume, regardless of their ploidy levels. The mitotic index in each line showed a maximum value of between 6-8% after about 5 days of subculture. Haploid cell lines of Kp9, Kp20 and Tp1 maintained haploid chromosome numbers (n=5) at high values (more than 90%) even after 620 days of subculture. However, the Kp42 line changed from the original haploid to the mixoploid by an increase in diploid cells during subculture. The diploid Kp10 and the mixoploid Tp4 lines retained their characteristic chromosome number throughout subculture. In the mixoploid Kp42 and the Tp4 lines, the cells having 5 or 10 diplochromosomes resulting from endoreduplication in a haploid or a diploid nucleus were occasionally found.
Three genes representing an indigenous (B1 gene for awn suppression), an alien (Hp gene for hairy peduncle from rye), and a lethal mutant gene (v1 for virescence), were transferred from common sources to a 6x (Triticumaestivum cv. S-615) and 4x wheat (T. durum var. reichenbachii), by repeated backcrosses using the latter as recurrent pollen parents. In every backcross generation, heterozygotes of each gene were backcrossed as well as self- pollinated, and the transmission rates of these genes to offspring weredetermined. The B1 gene showed normal transmission in both 6x and 4x wheats. The Hp gene was transmitted normally in 6x wheat, while its transmission rate was slightly depressed (ca. 10%) through both female and male gametes in 4x wheat. The v1 gene was transmitted at slightly lower frequency (about 10%) than its normal allele in 6x wheat, while its transmission rate was greatly reduced through both female (ca. 40%) and male gametes (ca. 70%) in 4x wheat. Thus, it was concluded that polyploidy increases tolerance of plants to deleterious genes.
Twenty-five meiotic mutants were selected from 281 sterile mutants induced by the treatment of the fertilized egg cells of rice with N-methy-N-nitrosourea. Of these, 19 were desynaptic and asynaptic mutants. In addition other meiotic mutants showing vacuolation of cytoplasm, incomplete cytokinesis, arrest of meiosis and degeneration and fused meiocytes were also obtained. Each of these mutants was governed by a single recessive gene.
Two strains of Hordeum bulbosum (4X), #191 and #487, were reciprocally crossed to a strain of H. vulgare (4X), D8/55, and their hybrid embryos were cytologically examined in order to know time, pattern and genetic control of somatic chromosome elimination occurred in the tetraploid hybrids between these species. Fourty hybrid embryos from each cross were sampled at 6 different times from 3 to 13 days after pollination. In all of the crosses, chromosome elimination occurred very frequently by about 9 days after pollination and a number of dihaploid cells were observed. The maximum rate of chromosome elimination was observed in the period of 3 to 5 days after pollination. It was cleary indicated that degree of chromosome elimination or dihaploid frequencies were quite different between the crosses with #191 and #487 but not different between reciprocals. This strongly suggests that the chromosome elimination is mainly controlled by nuclear gene (s) involved in bulbosum parents, but affected little by cytoplasms of these two species.
A program for the microcomputer, written with the programming language BASIC, to list bacterial strain stocks is described. The program allows the creation of a file of more than 5000 strains or 25000 markers and/or plasmids, and permits the file to be searched for strains carrying desired markers. The program can be supplied upon request to the authors.
In each stage of the developing embryo sac of Lilium longiflorum changes in the distribution of iron (ferric type) were cytochemically investigated by means of the Prussian blue reaction. The distribution of the granular blue deposits observed in the process of meiosis and mitosis indicates a close relationship between iron and the spindle body structure. Especially, in the 2nd 4-nucleate stage, the region between both triploid daughter nuclei, which corresponds to the region of a mass of connection fibers, carries much more deposits than other regions of the cytoplasm. None of the deposits were observed in the nuclei, chromosomes, and nucleoli in all the stages investigated. It appears that an embryo sac gets a supply of iron from nucellus cells as judges from the rise and fall of the deposit number in them. An assumption about iron contained in embryo sac is discussed.
Specific locus tests of the effects of N-ethyl-N-nitrosourea (ENU) on mouse spermatogonia using visible loci and hemoglobin beta-chain (Hbb) locus have been performed. Male wild-type (C3Hf/He) mice were injected intraperitoneally with ENU. Eight weeks after injection, the males were mated with tester strain females (PW) homozygous for six visible recessive genes. Ten visible and 2 hemoglobin mutants were obtained. The mutation frequency was 60.3×10-5/locus/generation. These mutations were all heritable, and nine out of ten mutations were viable under homozygous conditions. The results suggest that the mutations induced by ENU on spermatogonia of mice might have resulted from events at the genic rather than the chromosomal level.
Geographical distribution of some sibling species of Drosophila was explained by the direction of evolution based on the mating preferences and White′s stasipatric speciation. The D. bipectinata complex and the D. takahashii complex distributed in the Oriental-Australian biogeographic zones are good examples for the speciation model in which the sibling species repeatedly evolved in the center near Borneo and expanded radially, eliminating the old species.