Showing papers in "Journal of Genetics in 1988"
TL;DR: Genetic analysis was done on a number of nitrate tolerant supernodulating (nts) mutant soybean lines, finding a leaky mutant with partial autoregulation as its segregation ratios do not fall into any of the obvious patterns.
Abstract: Genetic analysis was done on a number of nitrate tolerant supernodulating (nts) mutant soybean lines. These lines are altered in the autoregulation response, and each was isolated as a separate mutational event following chemical mutagenesis. Crosses were made betweennts lines on a diallel pattern, and each was also crossed usingnts lines as female parent, to wild-type nodulation cultivars. F1 and F2 data were analysed from each cross for nodulation type and number. No complementation was noted wherents lines were intercrossed, suggesting that in each line the same gene was affected. Wherents lines were crossed with wild-type cultivars all the F1 progeny were wild-type, confirming that thenls gene is recessive and, with one exception,nts 1116, all of the F2 progeny segregated into a 3:1 wild-type to supernodulating phenotype, indicating that a single gene is involved. The hypernodulating linents 1116 gave a 1:1 ratio in its F2 progeny when crossed with othernts lines. This line behaved as a dominant in the latter crosses. No wild-type segregants were recovered, therefore again no complementation look place. This line may be a leaky mutant with partial autoregulation as its segregation ratios do not fall into any of the obvious patterns.
29 citations
TL;DR: The greater genotypic variability of holocyclic populations is due to recombination during the sexual phase, which is supported by the study of populations which revealed high genotypesic variability and homogeneity between populations in areas with harsh winters.
Abstract: Populations of the rose aphid (Macrosiphum rosae) from various latitudes show differences in their life cycles. In warm climates they are exclusively parthenogenetic, whereas in cold climates sexual reproduction allows the aphid to overwinter in the egg stage. In temperate zones both holocyclic and anholocyclic clones occur within the same population. It is assumed that the reproductive mode has consequences for the genotypic structure of the populations. Continuous parthenogenesis results in low genogypic variability caused by selection and/or random genetic drift. The greater genotypic variability of holocyclic populations is due to recombination during the sexual phase. This yiew is supported by the study of populations which revealed high genotypic variability and homogeneity between populations in areas with harsh winters (e.g. Norway). In temperate countries (e.g. England) the genotypic variability was lower but the uniformity between populations still high, and in warm climates (e.g. the Canary Isles) the variability was lowest and heterogeneity between populations largest.
25 citations
19 citations
TL;DR: The different regional and caste groups of India possessing diverse haplolype combinations provide an ideal opportunity to evaluate the selective values of these haplotypes and to study human immunogenetics.
Abstract: The HLA system may play an important role in natural selection processes through its involvement in immune response and because of the HLA association of some diseases. Linkage disequilibrium in the HLA system poses many interesting questions. India. a melting pot of races and cultures in sympatric isolation, provides an ideal opportunity to study these aspects. Linkage disequilibrium and haplotype data are valuable in the comparison of various populations. An analysis of the available HLA A-B haplotype data for the Indian population documents the heterogeneous nature of the latter: each endogamous caste group, major group or even regional group has its characteristic haplotype profile. The haplotypeA1-B17 is present in most Indian populations butA10-B8 occurs mostly in North India: this may be a consequence of founder effects. The haplotypeAl-B8 a typical Caucasian haplotype, is absent in the Indian subcontinent: this may be due to the selective disadvantageA1-B8 confers in the Indian environment. The different regional and caste groups of India possessing diverse haplolype combinations provide an ideal opportunity to evaluate the selective values of these haplotypes and to study human immunogenetics.
17 citations
TL;DR: An approach to quantifying the orientation of a cline is put forward, based on description of gene-frequency variance as a function of distance between populations, by means of directional variograms.
Abstract: Directional gene flow between genetically differentiated populations leads to parallel gene-frequency gradients at various loci; processes of differential selection are not expected to result in equally oriented patterns of gene frequencies. Therefore, inferences on the mechanisms maintaining genetic diversity can be drawn by comparing the directions of clines at different loci. An approach to quantifying the orientation of a cline is put forward here. The method is based on description of gene-frequency variance as a function of distance between populations, by means of directional variograms. The mean axis of the cline is then computed by averaging the directional components of variation; it can be regarded as the axis along which the frequencies of an allele vary showing the maximum degree of order. The significance of the mean axis can be tested, and the directions of two clines can be compared, using techniques developed in circular statistics. An example of application of this method to human gene frequencies is presented. Discordant clines are observed at six electrophoretically polymorphic loci in Eurasian populations. Only a fraction of such clines can be accounted for by the Neolithic radiation of early farmers in the Middle East and Europe.
14 citations
TL;DR: The mode of inheritance of resistance to green leafhopper in 12 cultivars of riceOryza saliva L. was studied, revealing that single dominant genes confer resistance in six varieties, two independent dominant genes in four varieties, and single recessive genes in two varieties.
Abstract: The mode of inheritance of resistance to green leafhopper in 12 cultivars of riceOryza saliva L. was studied. Seedlings of parent and hybrid populations were artificially infested with second- and third-instar virus-free green leafhopper nymphs. Seedling reaction was scored when TNI, the susceptible check, was completely killed. The results revealed that single dominant genes confer resistance in six varieties, two independent dominant genes in four varieties, and single recessive genes in two varieties. The single dominant genes in Sri Gaya, ARC 7320, and T23 and one of the two genes in Aswina and Bhura Rata 2 are allelic toGlh-1; while Bhawalia hasGlh-5 gene. The second gene of Bhura Rata 2 is allelic to IR28 gene. Resistance in Chamar is controlled by two independent genes one of which is allelic toGlh-5 and the other allelic to IR28 gene. Bazal hasGlh-2 andGlh-5. The single recessive gene in ARC 7012 is allelic toglh-4 but the single recessive gene in DV85 is nonallelic to and independent ofglh-4. This new recessive gene is designated asglh-8. The single dominant genes of Dumai, Gadur, and the second gene of Aswina are nonallelic to all the known genes for resistance.
14 citations
TL;DR: These in paraphrase are the questions that Max Delbriick poses' to himself at the beginning of his essay "Mind from Matter?".
9 citations
TL;DR: Genotypes from twelve accessions of five wild species from the genusMedicago were screened for callus formation and somatic embryogenesis using two tissue culture protocols and of the two pairs of reciprocal crosses tested here, one provided evidence of cytoplasmic inheritance of the trait, the other did not.
Abstract: Genotypes from twelve accessions of five wild species from the genusMedicago were screened for callus formation and somatic embryogenesis using two tissue culture protocols. These wild species were compared with two highly regenerable genotypes ofMedicago saliva. Embryogenesis for the wild types was very low. Wild species genotypes, which gave some callus production, were isolated.
8 citations
TL;DR: The FLP recombinase of the yeast 2 micron circle plasmid belongs to the Int family of recombinases and only three amino acid residues are invariant among members of this family as mentioned in this paper.
Abstract: The FLP recombinase of the yeast 2 micron circle plasmid belongs to theInt family of recombinases. Only three amino acid residues are invariant among members of this family. Functional analyses of FLP protein variants mutated at these three residues suggest their involvement at specific steps of the recombination pathway. We propose that these residues play the same functional role in the mechanism of action of all theInt family recombinases.
8 citations
TL;DR: Show that, in addition to the chromosomal instability, some hybrids display unstable expression of three genes borne on the kangaroo active maternal X chromosome, which may be co-ordinately inactivated at high frequency, then reactivated once more.
Abstract: Somatic cell hybrids between cells of widely divergent mammalian species display a range of chromosomal and genetic anomalies which may be the equivalent of the “genomic shock” phenomena observed in many plant and animal interspecific hybrids. Mouse-kangaroo hybrids show extreme segregation and fragmentation of the kangaroo chromosomes. Here 1 show that, in addition to the chromosomal instability, some hybrids display unstable expression of three genes borne on the kangaroo active maternal X chromosome. These genes (HPRT, G6PD andPGK) may be co-ordinately inactivated at high frequency, then reactivated once more. I suggest that this reversible inactivation in interspecific hybrids may be the result of an unstable change at an X inactivation centre located in the kangaroo Xq.
7 citations
TL;DR: The results suggest the presence of multiple (possibly identical) copies of the genome in A. vinelandii and an equilibrium between alleles of the same gene with and without the transposon was evident during random segregation.
Abstract: The genome ofAzotobacler vinelandii has been taggedin vivo with transposons. The cells have then been allowed to divide and the pattern of segregation of the genomes has been studied. The results suggest the presence of multiple (possibly identical) copies of the genome inA. vinelandii. Only a fraction of the total number of genomes seem to have been tagged with transposon and an equilibrium between alleles of the same gene with and without the transposon was evident during random segregation.
TL;DR: Results strongly indicate a cell-autonomous requirement for the product ofl(1)npr-1+.
Abstract: The 2B5 chromosomal locus inDrosophila contains a gene,I(1)npr-1
+, whose product required intrans for the expression of the larval salivary gland-specific geneSgs-3. We have addressed the question as to whether this factor acts in a cell-autonomous manner or not. This was made possible by the use of a transformant strain that makes anSgs-3-E. coli β-galactosidase (lacZ) fusion protein, under the control of anSgs-3 promoter, allowing the cellular examination of gene expression by a histochemical assay for enzyme activity. Using genetic methods, larvae that were mosaic for the loss of function mutationl(l)npr-1 were generated. The expression of theSgs-3-lacZ fusion gene was assayed histochemically in such larvae. Our results strongly indicate a cell-autonomous requirement for the product ofl(1)npr-1+. This is in contrast to another factor, the hormone ecdysterone, which is also required forSgs-3 expression, but acts in a non-autonomous manner
TL;DR: A positive regulatory gene has been cloned from Azotobacter vinelandii, using its ability to activate the expression of nifH: lacZ fusion in E. coli to activation the transcription from the P1 promoter of Rhizobium meliloti.
Abstract: A positive regulatory gene has been cloned fromAzotobacter vinelandii, using its ability to activate the expression ofnifH: lacZ fusion inE. coli. The gene has also been shown to activate the transcription from the P1 promoter ofRhizobium meliloti. It did not, however, hybridize with thenifA gene ofR. meliloti.
TL;DR: Three methods for rapidly distinguishing mutations in the three complementation groups of Dictyostelium discoideum are demonstrated and it is shown that nys C and non-nys C mutants can be distinguished on the basis of the Lieberman-Burchard color reaction for sterols.
Abstract: Spontaneous nystatin resistance mutations inDictyostelium discoideum fall into three complementation groups;nys A. nys B andnys C. We demonstrate three methods for rapidly distinguishing mutations in the three complementation groups. In the first methodnys B andnys C mutations are identified by their sensitivity to the sterol biosynthesis inhibitors azasterol A25822B and fenarimol respectively. The second method exploits the differential sensitivities of thenys mutations to the polyene antibiotic pimaricin. In the last method we show thatnys C and non-nys C mutants can be distinguished on the basis of the Lieberman-Burchard color reaction for sterols.
TL;DR: It is suggested that interspecific cell hybrids are predisposed to gene amplification and may also show many other types of genetic and chromosomal instability, possibly thein vitro equivalent of the “genomic shock” phenomena described for interstrain or interspecies hybrids of plants or animals.
Abstract: In order to investigate instances of genetic instability in divergent cell hybrids, we studied several RAT-resistant colonies recovered from fusions between HPRT or TK-deficient rodent cells and marsupial or monotreme cells. Most of these colonies proved to lack HPRT or TK activity and to have survived by acquiring resistance to aminopterin; such aminopterin-resistant lines were never recovered from parent cells subjected to HAT selection. Two of the aminopterin-resistant hybrids over-produced DHFR, and possessed either double minutes or an abnormally banded region, the cytological manifestations of gene amplification. Selection in higher aminopterin concentrations yielded a highly resistant line with 100X wild-type DHFR activity and a large homogeneously staining region. We suggest that interspecific cell hybrids are predisposed to gene amplification and may also show many other types of genetic and chromosomal instability, possibly thein vitro equivalent of the “genomic shock” phenomena described for interstrain or interspecies hybrids of plants or animals.
TL;DR: It is suggested either that the hamster β-tubulin gene is repressed in hybrids, or that hamster €tubulin is excluded from the spindle in hybrid cells.
Abstract: A Colcemid-resistant Chinese hamster line with an altered form of β-tubulin was used in studies of the expression of spindle proteins in interspecific cell hybrids. Eight hybrids between this line, and a Colcemid-sensitive mouse cell line, were studied. The altered hamster β-tubulin was not expressed as an increased resistance to Colcemid in any hybrid. Since the complete hamster chromosome complement was represented among the hybrids, the absence of altered β-tubulin is not due to segregation of the mutant hamster β-tubulin gene. We suggest either that the hamster β-tubulin gene is repressed in hybrids, or that hamster β-tubulin is excluded from the spindle in hybrid cells. We compare these findings with previous reports of the repression of other highly active, moderately repeated constitutive genes in interspecific hybrids.
TL;DR: It was brought out that additive genetic variance defined essentially for one gene does not extendper se to multi-gene systems.
Abstract: Following the Fisherian approach, the expression for additive genetic variance is derived in a single gene system through a regression equation in two variables which are used to obtain the additive and dominance variances. The approach is extended to two genes with restricted linkage and inbreeding. It was brought out that additive genetic variance defined essentially for one gene does not extendper se to multi-gene systems.
TL;DR: Fusion and regeneration of the spheroplasts were attempted using drug resistant mutant strains of M. smegmalis and simultaneous expression of rccombinant properties was observed only after an initial lag in the isolated clones.
Abstract: Mycobacterial spheroplasts were prepared by treatment of the glycinesensitized cells with a combination of lipase and lysozyme. They were stable for several hours at room temperature but were lysed on treatment with 0.1% sodium dodecyl sulfate. The spheroplasts could be regenerated on a suitable medium. Fusion and regeneration of the spheroplasts were attempted using drug resistant mutant strains ofM. smegmalis. Recombinants were obtained from spheroplast fusion mediated by polyethylene glycol and dimethyl sulfoxide. Simultaneous expression of rccombinant properties was observed only after an initial lag in the isolated clones. This has been explained as due to “chromosome inactivation” in the fused product.
TL;DR: Reduction in AmpR transformants is intermediate (30 to 100-fold lower) in strain N19 with pJ18StrR38 and pD7, interpreted to suggest the presence of a small “aberration” in thenov region.
Abstract: Chromosomal DNAcarrying closely-linked genetic marker allelesstrrnovr produces roughly equivalent number of StrR (streptomycin-resistant) and NovR (novobiocin-resistant) transformants from wild type strain but widely differnt ratios (StrR50: NovR1) from a mutant strain N19. Reduction in AmpR (vector marker) extra chromosomal transformants is observed in N19 with chimeric plasmids carrying chromosomal DNA inserts fromnov region. Thus, AmpR transformants with chimeric plasmid DNA pJl-8N2 and pJl-8N19 are two to three orders of magnitude lower in N19 than in wild type. However, pJl-8NaIR33, pKuvrl, p3 and p10 DNA transform N19 and Rd with near-equal efficiency. Reduction in AmpR transformants is intermediate (30 to 100-fold lower) in strain N19 with pJ18StrR38 and pD7. These data are interpreted to suggest the presence of a small “aberration” in thenov region.
TL;DR: It is seen that for a wide range of model parameters (deme size, distribution of male quality, local resource level), multiple mating leads to a considerable increase in the fitness.
Abstract: When there is a variation in the quality of males in a population, multiple mating can lead to an increase in the genetic fitness of a female by reducing the variance of the progeny number. The extent of selective advantage obtainable by this process is investigated for a population subdivided into structured demes. It is seen that for a wide range of model parameters (deme size, distribution of male quality, local resource level), multiple mating leads to a considerable increase in the fitness. Frequency-dependent selection or a stable coexistence between polyandry and monandry can also result when the possible costs involved in multiple mating are taken into account.