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[Phage T4 partial diploidy obtained with the method of DNA interrupted injection. I. Analysis of the genetic structure and phage progeny reproduction process].

Phage T4 chromosome fragmentation is shown to take place when DNA injection is interrupted, a fragment length being strictly controlled by the interval from the moment of adsorbtion till the moment of an interruption. Populations of the bacteria cells infected by the phage T4 partial diploids are produced with the method of DNA interrupted injection. In the population a merodiploid involves some phage T4 amber mutant and a phage "wild" type chromosome fragment of the size controlled. To construct merodiploids the amber mutant in gene 43 and the mutant in gene 32 with the higher and the lower recombination frequency, accordingly, are used. Every merodiploid which is the heterozygote by one of these genes or which is the heterozygote by the late genes is determined to reproduce mixed phage progeny. Both the mean of the burst and the parent genotypes ratio in progeny either in the E. coli CR-63 cells or in the E. coli B depend on neither the heterozygote genetic structure nor the diploid region size. The results obtained conclude that phage genes express their function in the small fragments and the fragment recombination with the mutant partner whole chromosome follows their autonomous replication.

Chromosomes↗
PubMed2005

Testing for clonal propagation.

The conceptual basis for testing clonal propagation is reconsidered with the result that two steps need to be distinguished clearly: (1) specification of the characteristics of multilocus genotype frequencies that result from sexual reproduction together with the kinds of deviations from these characteristics that are produced by clonal propagation, and (2) a statistical method for detecting these deviations in random samples. It is pointed out that a meaningful characterization of sexual reproduction reflects the association of genes in (multilocus) genotypes within the bounds set by the underlying gene frequencies. An appropriate measure of relative gene association is developed which is equivalent to a multilocus generalization of the standardized gametic disequilibrium (linkage disequilibrium). Its application to the characterization of sexually produced multilocus genotypes is demonstrated. The resulting hypothesis on the frequency of a sexually produced genotype is tested with the help of the (significance) probability of obtaining at least two copies of the genotype in question in a random sample of a given size. If at least two copies of the genotype are observed in a sample, and if the probability is significant, then the hypothesis of sexual reproduction is rejected in favor of the assumption that all copies of the genotype belong to the same clone. Common testing approaches rest on the hypothesis of completely independent association of genes in genotypes and on the (significance) probability of obtaining at least as many copies of a genotype as observed in a sample. The validity of these approaches is discussed in relation to the above considerations and recommendations are set out for conducting appropriate tests.

Genetics, Population↗
PubMed2006

Degeneration after sexual differentiation in hydra and its relevance to the evolution of aging.

Aging occurs in most multicellular animals, yet some primitive animals do not show any sign of aging. This raises the following question: How have metazoans acquired the trait of aging in the course of evolution? Comparative studies of various species have provided a clue to this question by showing that sexually reproducing organisms predominantly undergo aging. The evolutionary theory "pleiotropy" also postulates aging as a price for facilitating the reproduction in the early life stage of an organism. For investigating the association between sexual reproduction and aging, a sexual phase-inducible organism in a laboratory would be suitable. One of such organisms is hydra, a genus of Cnidaria. Asexual hydra has been considered to be immortal, but there is the possibility that hydra undergoes aging after sexual reproduction. To search for signs of aging in hydra, we studied sexually differentiated Hydra oligactis at the individual and cellular levels. As a result, we found a significant decline in the capacities for food capture, contractile movements, and reproduction. More importantly, we discovered an exponential increase in the mortality rate of the population. These observations suggest that the degenerative process in H. oligactis represents the aging process. Furthermore, we found that the number of germ cells increased, whereas the number of somatic cells concomitantly decreased. The observed change of the cell composition is thus consistent with the "pleiotropy" theory of aging.

Animals↗
PubMed1998

Transgenic approaches to the increase of disease resistance in farm animals.

Molecular genetics and reproductive biology techniques enable the transfer of foreign DNA into mammals. Novel approaches to modify disease resistance or susceptibility in livestock are justified by economic and animal welfare concerns. Current research on the improvement of disease resistance by gene transfer focuses on three main strategies, as follows: a) somatic gene transfer, i.e., nucleic acid vaccines b) deletive germ-line gene transfer, i.e., gene knockout c) additive germ-line gene transfer. These strategies aim at either the transient or stable expression of components known to influence non-specific or specific host defence mechanisms, or the disruption of genes known to cause susceptibility to disease. Referring to the source of the effective agent and the site and mode of action, the strategies are termed 'genetic', 'congenital', 'intracellular' and 'extracellular' immunisation. Each gene transfer experiment has to be evaluated carefully with respect to the potential to create novel cases of pathogen resistance or to lose species barriers or cell-type restrictions.

Animals↗
PubMed2003

Gene testing: what the health professional needs to know.

Physicians and health professionals are faced with new challenges in the era of increasing information on genetics and health. The sequencing of the human genome has created more opportunities for genetic research and increased awareness of the role of genes in diseases. There is also an increased awareness of genetic susceptibility and gene testing. As a result of the advances in genetic research, the public demand for gene testing is on the rise. Patients are now seeking more information about inheritable diseases and predisposition to genetically related disease from doctors and other health professionals. Genetic tests are often conducted to confirm the diagnosis of a genetic disease as well as to assess genetic risk, predict response to drugs, and assist in reproductive decision making. Genetic tests are available for over 950 inherited diseases or conditions in the GeneTests data base for clinical or research purposes. A number of challenges face health professionals when using genetic tests for diagnosis, predictive testing, or reproductive decision making. These include the constant change in genetics knowledge and the increased demand to keep up with the various aspects of the genetic testing process. To meet these demands, physicians and other health professionals should use available educational genetic resources to provide adequate patient care.

Chromosome Mapping↗
PubMed2005

Evaluation of glucose metabolism and reproductive hormones in polycystic ovary syndrome on the basis of peroxisome proliferator-activated receptor (PPAR)-gamma2 Pro12Ala genotype.

BACKGROUND: Peroxisome proliferator-activated receptor (PPAR)-gamma2 Pro12Ala polymorphism has been suggested as a protective factor for polycystic ovary syndrome (PCOS). In this study, we aimed to investigate metabolic features and reproductive hormones in women with PCOS and compare these features with control women on the basis of Pro12Ala genotype. METHODS: This study involved 60 randomly selected women with PCOS and 60 controls. Main outcome measures were anthropometric measures, variables of glucose metabolism and reproductive hormones. All the patients were genotyped for Pro12Ala variant of PPAR-gamma2 gene. RESULTS: Patients with Pro12Ala polymorphism were more obese in both groups. Furthermore, they had lower fasting insulin levels, were less insulin-resistant and were less glucose-intolerant as demonstrated by 2 h glucose concentrations. However, there was no difference in reproductive hormone levels on the basis of Pro12Ala genotype. CONCLUSIONS: Both control women and women with PCOS had significant differences in glucose metabolism on the basis of PPAR-gamma2 Pro12Ala polymorphism. Pro12Ala variant may break the process that leads to PCOS in susceptible women, instead of being a direct causal relationship between Pro12Ala polymorphism and PCOS.

Adult↗
PubMed2002

Differential lipid biosynthesis underlies a tradeoff between reproduction and flight capability in a wing-polymorphic cricket.

The biochemical basis of life-history tradeoffs is a poorly studied aspect of life-history evolution. We used radiotracer and endocrine approaches to investigate the extent to which morphs of a wing-polymorphic insect differ in the biosynthesis of lipid classes important for dispersal capability vs. reproduction (ovarian growth). The flight-capable genotype of Gryllus firmus biosynthesized a greater amount of total lipid and triglyceride (main flight fuel), which was preferentially allocated to somatic tissue during early adulthood. By contrast, the flightless genotype biosynthesized a significantly greater amount of phospholipid (important in egg development), which was preferentially allocated to ovaries. Topical application of a juvenile-hormone mimic to the flight-capable morph caused it to express all aspects of lipid metabolism seen in the flightless morph. Differences in biosynthesis between morphs (i) occur coincident with 100-400% greater ovarian growth in the flightless morph, (ii) result from alterations of both de novo biosynthesis of fatty acid and downstream partitioning of fatty acids into triglyceride vs. phospholipid, and (iii) possibly result from genetically polymorphic hormonal regulators with negative pleiotropic effects on lipid biosynthesis and ovarian growth. The present study provides direct documentation of genetically based alterations of in vivo flux through pathways of intermediary metabolism leading to the differential production of end products central to the specialization of phenotypes for alternate life histories.

Animals↗
PubMed2005

Same-sex mating and the origin of the Vancouver Island Cryptococcus gattii outbreak.

Genealogy can illuminate the evolutionary path of important human pathogens. In some microbes, strict clonal reproduction predominates, as with the worldwide dissemination of Mycobacterium leprae, the cause of leprosy. In other pathogens, sexual reproduction yields clones with novel attributes, for example, enabling the efficient, oral transmission of the parasite Toxoplasma gondii. However, the roles of clonal or sexual propagation in the origins of many other microbial pathogen outbreaks remain unknown, like the recent fungal meningoencephalitis outbreak on Vancouver Island, Canada, caused by Cryptococcus gattii. Here we show that the C. gattii outbreak isolates comprise two distinct genotypes. The majority of isolates are hypervirulent and have an identical genotype that is unique to the Pacific Northwest. A minority of the isolates are significantly less virulent and share an identical genotype with fertile isolates from an Australian recombining population. Genotypic analysis reveals evidence of sexual reproduction, in which the majority genotype is the predicted offspring. However, instead of the classic a-alpha sexual cycle, the majority outbreak clone appears to have descended from two alpha mating-type parents. Analysis of nuclear content revealed a diploid environmental isolate homozygous for the major genotype, an intermediate produced during same-sex mating. These studies demonstrate how cryptic same-sex reproduction can enable expansion of a human pathogen to a new geographical niche and contribute to the ongoing production of infectious spores. This has implications for the emergence of other microbial pathogens and inbreeding in host range expansion in the fungal and other kingdoms.

Animals↗
PubMed2002

Ped gene deletion polymorphism frequency in wild mice.

The Ped gene influences the rate of cleavage of preimplantation embryos and their subsequent survival. Embryos that express the product of the Ped gene, Qa-2 protein, cleave at a faster rate than embryos with an absence of Qa-2 protein. In addition, the Ped gene has pleiotropic effects on reproduction. Thus, there is a reproductive advantage to those mouse strains that are Qa-2 positive. The presence or absence of Qa-2 is reflected at the DNA level by the presence or absence (deletion polymorphism) of the gene(s) encoding Qa-2 protein. Many inbred and wild-derived mouse strains have been characterized as Qa-2 positive or negative, but no previous studies have looked at the distribution of the Ped gene in a population of free-living wild mice. The purpose of this study was to determine the Ped gene deletion polymorphism frequency in a sample of free-living wild mice. Twenty-nine mice were collected and identified as Mus musculus. Genomic DNA extraction was performed on tail tips, and PCR was used to amplify a region from the Ped gene. Known Qa-2 positive and negative mice were used as controls. Results showed that all 29 wild mice were positive for the Ped gene. Since the Ped gene is dominant and provides a reproductive advantage, it is not surprising that all of the wild mice were Qa-2 positive. However, our assay could not distinguish homozygous from heterozygous mice. It is possible that the Qa-2 deletion polymorphism is segregating in the population, and a larger sample size would identify some Qa-2 negative mice.

Adaptation, Physiological↗
PubMed2006

A genomic comparison of faster-sex, faster-X, and faster-male evolution between Drosophila melanogaster and Drosophila pseudoobscura.

A genomic comparison of Drosophila melanogaster and Drosophila pseudoobscura provides a unique opportunity to investigate factors involved in sequence divergence. The chromosomal arrangements of these species include an autosomal segment in D. melanogaster which is homologous to part of the X chromosome in D. pseudoobscura. Using orthologues to calculate rates of nonsynonymous (d(N)) substitutions, we found genes on the X chromosome to be significantly more diverged than those on the autosomes, but it is not true for segment 3L-XR which is autosomal in D. melanogaster (3L) and X-linked in D. pseudoobscura (XR). We also found that the median d(N) values for genes having reproductive functions in either the male, the female, or both sexes are higher than those for sequences without reproductive function and even higher for sequences involved in male-specific function. These estimates of divergence for male sex-related sequences are most likely underestimates, as the very rapidly evolving reproductive genes would tend to lose homology sooner and thus not be included in the comparison of orthologues. We also noticed a high proportion of male reproductive genes among the othologous genes with the highest rates of d(N). Reproductive genes with and without an orthologue in D. pseudoobscura were compared among D. melanogaster, D. simulans, and D. yakuba and it was found that there were in fact higher rates of divergence in the group without a D. pseudoobscura orthologue. These results, from widely separated taxa, bolster the thesis that sexual system genes experience accelerated rates of change in comparison to nonsexual genes in evolution and speciation.

Animals↗
PubMed1985

The evolutionary role of recombinational repair and sex.

We have argued that sexual reproduction arose very early in the evolution of life as a way of overcoming informational damage or loss through recombinational repair. As organisms became more complex and genome information content expanded, diploidy, at first transient, became the predominant way of coping with increased vulnerability to mutation. This allowed further genome expansion. Once such expansion had occurred, however, diploidy became essentially irreversible, since reversion to haploidy would lead to expression of accumulated deleterious recessive alleles. This expression of recessive alleles also imposes a stiff penalty on organisms that experiment with close inbreeding forms of recombinational repair. A consequence of sex is that fitness (defined as per capita rate of increase) is density dependent. At low population density, fitness declines due to increased costs of finding a mate. This fundamental constraint on population increase can inhibit evolutionary success of the best adapted species if it is small in numbers. Sexual reproduction also tends to eliminate new coadapted genotypes within a species by breaking up their coadapted gene complexes; this also contributes to the cohesion of species. In general, we think the existence of species and their characteristic cohesion and stability over time are direct consequences of sex; and sex in turn is a consequence of the need to overcome gene damage through recombinational repair while at the same time masking the deleterious effects of mutation.

Animals↗
PubMed1985

The maintenance of polymorphism owing to differences in developmental time and competition.

The effect of developmental time on the maintenance of an enzyme polymorphism is analyzed under the assumption that competition exists for a reproductively essential resource. Specifically, in laboratory vials Drosophila compete for oviposition and pupation sites. This system of competition serves as a prototype for the model with late-eclosing individuals being excluded from the reproductive pool. Two mating behaviors are modelled: (i) mating is with individuals from only the same cohort group and occurs only once, and (ii) mating is with all individuals that have eclosed up to that time and occurs daily. Numerical analyses are done on both mating structures using data from Drosophila mercatorum. The simulations show that mating structure and initial conditions do not affect the equilibrium genotype frequencies, but that slight changes in the level of competition can dramatically alter the equilibrium values.

Alcohol Dehydrogenase↗
PubMed2000

The phylogeny of closely related species as revealed by the genealogy of a speciation gene, Odysseus.

Molecular differentiation between races or closely related species is often incongruent with the reproductive divergence of the taxa of interest. Shared ancient polymorphism and/or introgression during secondary contact may be responsible for the incongruence. At loci contributing to speciation, these two complications should be minimized (1, 2); hence, their variation may more faithfully reflect the history of the species' reproductive differentiation. In this study, we analyzed DNA polymorphism at the Odysseus (OdsH) locus of hybrid sterility between Drosophila mauritiana and Drosophila simulans and were able to verify such a prediction. Interestingly, DNA variation only a short distance away (1.8 kb) appears not to be influenced by the forces that shape the recent evolution of the OdsH coding region. This locus thus may represent a test case of inferring phylogeny of very closely related species.

Animals↗
PubMed1983

Effects of the sex-linked dwarfing gene (dw) on growth and reproduction in white Leghorn hens.

The influence of the dwarfing gene, dw, on growth and reproduction was determined by comparing 1) pure line and reciprocal cross dwarf and normal layers and 2) dwarf and normal full-sib sisters. In Experiment 1, two lines of chickens, the Oregon State University randombred dwarf Leghorn population (D) and Shaver Starcross "288" Leghorns (S), were mated within line and reciprocally to produce normal-sized (SS, SD) and dwarf (DS, DD) female progeny. All progeny were reared similarly until 18 weeks of age when birds were transferred to individual cages. At 18 weeks of age, half the pullets were fed a basal laying ration containing 15% protein while the remaining birds received the basal ration with .1% supplemental methionine. In Experiment 2, full-sib normal and dwarf sisters were obtained by mating hemizygous dwarf females to heterozygous males. Layers were reared in a similar manner to those in Experiment 1 with the exception that all layers received the basal ration with .1% methionine supplemented. Methionine supplementation in Experiment 1 significantly increased egg weights at 35 and 62 weeks of age for all lines and crosses but had no effect on other growth and reproductive traits. Genotype X diet interactions were not observed for any of the measured traits. Normal-sized layers had significantly heavier body weights and longer shank lengths than dwarf layers in both experiments. Dwarf hens in both experiments showed reduced egg production capabilities, although ages at sexual maturity were similar among phenotypes. Dwarf layers laid smaller eggs than normal-sized layers. There were no consistent differences in feed efficiency measures between normals and dwarfs.

Animals↗
PubMed2006

Changes in reproductive function and white blood cell proliferation induced in mice by injection of a prolactin-expressing plasmid into muscle.

Prolactin (PRL) is a pituitary hormone involved in various physiological processes, including lactation, mammary development, and immune function. To further investigate the in vivo and comparative endocrine roles of PRL, mouse PRL cDNA fused to the cytomegalovirus promoter, was introduced into muscle by direct injection. Previously we studied the function of rat PRL using the same protocol. PRL mRNA was detected in the muscle following injection by RT-PCR and subsequent Southern blot analysis. PRL was also detected and Western blot analysis revealed a relatively high level of serum PRL. In the pCMV-mPRL-injected female mice, the estrous cycle was extended, especially in diestrus stage and the uterus thickening that was shown in normal estrous stage was not observed. In the pCMV-mPRL-injected male mice, new blood vessels were first found at 5 weeks of age and fully developed blood vessels were found after 8 weeks in the testis. The number of Leydig cells increased within the testis and the testosterone level in serum was observed high. Finally, the number of white blood cells (WBCs) increased in the pCMV-mPRL-injected mice. The augmentation of WBCs persisted for at least 20 days after injection. When injection was combined with adrenalectomy, there was an even greater increase in number of WBCs, especially lymphocytes. This increase was returned normal by treatment with dexamethansone. Taken together, our data reveal that intramuscularly expressed mouse PRL influences reproductive functions in female, induces formation of new blood vessels in the testis, and augments WBC numbers. Of notice is that the Leydig cell proliferation with increased testosterone was conspicuously observed in the pCMV-mPRL-injected mice. These results also suggest subtle difference in function of PRL between mouse and rat species.

Animals↗
PubMed2005

The evolutionary forces maintaining a wild polymorphism of Littorina saxatilis: model selection by computer simulations.

Two rocky shore ecotypes of Littorina saxatilis from north-west Spain live at different shore levels and habitats and have developed an incomplete reproductive isolation through size assortative mating. The system is regarded as an example of sympatric ecological speciation. Several experiments have indicated that different evolutionary forces (migration, assortative mating and habitat-dependent selection) play a role in maintaining the polymorphism. However, an assessment of the combined contributions of these forces supporting the observed pattern in the wild is absent. A model selection procedure using computer simulations was used to investigate the contribution of the different evolutionary forces towards the maintenance of the polymorphism. The agreement between alternative models and experimental estimates for a number of parameters was quantified by a least square method. The results of the analysis show that the fittest evolutionary model for the observed polymorphism is characterized by a high gene flow, intermediate-high reproductive isolation between ecotypes, and a moderate to strong selection against the nonresident ecotypes on each shore level. In addition, a substantial number of additive loci contributing to the selected trait and a narrow hybrid definition with respect to the phenotype are scenarios that better explain the polymorphism, whereas the ecotype fitnesses at the mid-shore, the level of phenotypic plasticity, and environmental effects are not key parameters.

Animals↗
PubMed2003

Apomixis in the interspecific triploid hybrid fern Cornopteris christenseniana (Woodsiaceae).

Cornopteris christenseniana is a "sterile" interspecific triploid hybrid of diploid C. crenulatoserrulata and tetraploid C. decurrenti-alata. Morphological and cytological studies show that, of 41 young plants of Cornopteris that have been propagated naturally in the Fern Garden of the Botanical Gardens, University of Tokyo, 30 plants are the sterile C. christenseniana, 10 are fertile C. decurrenti-alata and 1, fertile C. crenulatoserrulata. This proportion supports the view that the young plants of C. christenseniana are derived from spores of reproductively mature plants of the species cultivated. Cytogenetic observations and culture experiments show that C. christenseniana produces normal spores in various proportions in some sporogenetic pathways that are aberrant from the ordinary process in sexual and apomictic ferns. Under culture conditions, normal spores germinate in rough proportion to the frequency of normal spores, and sporophytes are apogamously produced in rough proportion to the frequency of spore germination. As a whole, the rates of spore germination and apogamous sporophyte development vary according to the specific plant. Taken together, these observations suggest that C. christenseniana is an incipient apomict.

Chromosomes, Plant↗
PubMed2004

Molecular evidence for the hybrid origin of species in the soft coral genus Alcyonium (Cnidaria: Anthozoa: Octocorallia).

Several recent studies have suggested that hybridization may play a previously unrecognized and important role in the evolution of corals. Our observations of polymorphic and recombinant sequences in the multicopy ribosomal internal transcribed spacer (ITS) region suggested the possible hybrid origin of two European soft coral species, Alcyonium hibernicum and Bellonella bocagei. To examine this possibility further we cloned and sequenced ITS-1 from multiple individuals and populations of these two species as well as two sympatric congeners, A. coralloides and A. sp. M2. Phylogenetic analyses separated the observed sequence variants into two distinct clades. All A. coralloides sequences belonged to clade A, while A. sp. M2 had only clade B sequences. A majority of A. hibernicum individuals, however, contained both clade A and B sequences that were identical to the predominant sequence variants found in A. coralloides and A. sp. M2, respectively. This pattern of additivity suggests that A. hibernicum originated from a hybrid cross between A. coralloides and A. sp. M2, a hypothesis that is supported by its unusual mode of reproduction (meiotic parthenogenesis). The predominant sequence variant found in B. bocagei was a unique, derived clade B sequence; in addition, however, most individuals of this species also had copies of a sequence identified as a recombinant between clade A and clade B sequence types. The presence of this recombinant sequence in the B. bocagei genome suggests that this species may also be the product of past hybridization events within the clade. Reticulate evolution may explain the failure of several previous studies to resolve the phylogeny of these four species.

Animals↗