Abstract

Understanding the prevalence of sexual reproduction in eukaryotes is a hard problem. At least two aspects still defy a fully satisfactory explanation, the functional significance of genetic recombination and the great variation among taxa in the relative lengths of the haploid and diploid phases in the sexual cycle. We have performed an experimental study to explore the specific advantages of haploidy or diploidy in the ...

Abstract

BACKGROUND:While the genetics of diploid inheritance are well studied and software for linkage mapping, haplotyping and QTL analysis are available, for tetraploids the available tools are limited. In order to develop such tools it would be helpful if simulated populations based on a variety of models of the tetraploid meiosis would be available.RESULTS:Here we present PedigreeSim, a software package that simulates meiosis in both diploid and tetraploid species and uses this to simulate pedigrees and cross populations. For tetraploids a variety ...

Abstract

We generated all possible haploid and homozygous diploid genotypes at 6 biosynthetic loci in yeast and scored their fitness to examine whether there was any pattern of weak synergistic epistasis, which is a requirement of the deterministic mutation model for the evolution of sex. We measured 4 components of fitness: haploid growth rate, haploid mating efficiency, diploid growth rate, and diploid sporulation efficiency. We found that in agreement with previous work in yeast, epistasis tended to be small in magnitude and ...

Abstract

Ploidy varies tremendously within and between species, yet the factors that influence when or why ploidy variants are adaptive remains poorly understood. Our previous work found that diploid individuals repeatedly arose within ten replicate haploid populations of Saccharomyces cerevisiae, and in each case we witnessed diploid takeover within 1800 asexual generations of batch culture evolution in the lab. The character that allowed diploids to rise in frequency within haploid populations remains unknown. Here we present a number of experiments conducted with ...

Abstract

Molecular adaptation is typically assumed to proceed by sequential fixation of beneficial mutations. In diploids, this picture presupposes that for most adaptive mutations, the homozygotes have a higher fitness than the heterozygotes. Here, we show that contrary to this expectation, a substantial proportion of adaptive mutations should display heterozygote advantage. This feature of adaptation in diploids emerges naturally from the primary importance of the fitness ...

Abstract

Although seed plants and multicellular animals are predominantly diploid, the prominence of diploidy varies greatly among eukaryote life cycles, and no general evolutionary advantage of diploidy has been demonstrated. By doubling the copy number of each gene, diploidy may increase the rate at which adaptive mutations are produced. However, models suggest that this does not necessarily accelerate adaptation by diploid populations. We tested model predictions regarding rates of adaptation using asexual yeast populations. Adaptive mutations were on average partially recessive. As ...

Abstract

The role of genetic factors in extinction is firmly established for diploid organisms, but haplodiploids have been considered immune to genetic load impacts because deleterious alleles are readily purged in haploid males. However, we show that single-locus complementary sex determination ancestral to the haplodiploid Hymenoptera (ants, bees, and wasps) imposes a substantial genetic load through homozygosity at the sex locus that results in the production of inviable or sterile diploid males. Using stochastic modeling, we have discovered that diploid male production ...

Abstract

Contemporary sequencing studies often ignore the diploid nature of the human genome because they do not routinely separate or 'phase' maternally and paternally derived sequence information. However, many findings — both from recent studies and in the more established medical genetics literature — indicate that relationships between human DNA sequence and phenotype, including disease, can be more fully understood with phase information. Thus, the existing technological impediments to obtaining phase information must be overcome if human genomics is to reach ...

Abstract

Abstract Despite a great deal of theoretical attention, we have limited empirical data about how ploidy influences the rate of adaptation. We evolved isogenic haploid and diploid populations of Saccharomyces cerevisiae for 200 generations in seven different environments. We measured the competitive fitness of all ancestral and evolved lines against a common competitor and find that in all seven environments, haploid lines adapted faster than diploids, significantly so in three environments. We apply theory that relates the rates of adaptation and ...

Abstract

Senescence or ageing is an increase in mortality and/or decline in fertility with increasing age. Evolutionary theories predict that ageing or longevity evolves in response to patterns of extrinsic mortality or intrinsic damage. If ageing is viewed as the outcome of the processes of behaviour, growth and reproduction then it should be possible to predict mortality rate. Recent developments have shown that it is now possible to integrate these ecological and physiological processes and predict the shape of mortality trajectories. By ...

Abstract

Multiple functional queens in a colony (polygyny) and multiple mating by queens (polyandry) in social insects challenge kin selection, because they dilute inclusive fitness benefits from helping. Colonies of the ant Plagiolepis pygmaea brash contain several hundreds of multiply mated queens. Yet, within-colony relatedness remains unexpectedly high. This stems from low male dispersal, extensive mating among relatives and adoption of young queens in the natal colony. We investigated whether inbreeding results from workers expelling foreign males, and/or from preferential mating between ...

Note (first note only)

ISI Document Delivery No.: 519RR Times Cited: 0 Cited Reference Count: 67 Thurin, N. Aron, S. Belgian Fond National de la Recherche Scientifique (FRS-FNRS) We thank K. Trontti and L. Sundstrom for fruitful discussions on inbreeding in P. pygmaea, and P. Mardulyn for critical reading of a first draft of the manuscript. Thanks also to J. Evraerts for his help in laboratory. This work was supported by several grants from the Belgian Fond National de la Recherche Scientifique (FRS-FNRS) to NT and SA. WILEY-BLACKWELL PUBLISHING, INC MALDEN

Abstract

In social Hymenoptera (ants, bees, and wasps), the number of males that mate with the same queen affects social and genetic organization of the colony. However, the selective forces leading to single mating in certain conditions and multiple mating in others remain enigmatic. In this study, I investigated whether queens of the wood ant Formica paralugubris adopting different dispersal strategies varied in their mating frequency (the number of males with whom they mated). The frequency of multiple mating was determined by ...

Note (first note only)

64 BLACKWELL SCIENCE LTD OXFORD 117JX

Abstract

Polyploidization, the addition of a complete set of chromosomes to the genome, represents one of the most dramatic mutations known to occur. Nevertheless, polyploidy is well tolerated in many groups of eukaryotes. Indeed, the majority of flowering plants and vertebrates have descended from polyploid ancestors. This Review examines the short-term effects of polyploidization on cell size, body size, genomic stability, and gene expression and the long-term effects on rates of evolution. ...

Abstract

Trophic polymorphisms are a prominent form of phenotypic diversification in many animal taxa. Northern temperate lakes have become model systems for the investigation of sympatric speciation due to trophic polymorphisms. Many examples of niche-based phenotypic variation occur in temperate lakes, whereas northern rivers offer few such examples. To further investigate the conditions under which trophic polymorphisms are likely to evolve, the present study examined phenotypic variation related to snout size and shape in the mountain whitefish (Salmonidae: Prosopium williamsoni), which has ...

Note (first note only)

Whiteley, Andrew R.

Abstract

A problem involving the relationships between chromosome number and the degree of winter hardiness in the higher plants is outlined. A scale of relative degree of winter hardiness was constructed in order to compare the resistance to cold of related species belonging to families ranging from the temperate zone to the tropics. The data so far obtained have been arranged in an extensive table, and show the author's chromosome number determinations of 100 species and varieties of angiosperms, with a comparison ...

Abstract

10.1098/rspb.2000.1194 Evolutionary branching is the process whereby an initially monomorphic population evolves to a point where it undergoes disruptive selection and splits up into two phenotypically diverging lineages. We studied evolutionary branching in three models that are ecologically identical but that have different genetic systems. The first model is clonal, the second is sexual diploid with additive genetics on a single locus and the third is like the second but with an additional locus for mate choice. Evolutionary branching occurred under ...

Abstract

In an asexual population two favorable mutants can be incorporated into the population only if one occurs in a descendant of the individual in which the other occurred. In a sexual population both mutants can be incorporated through recombination. A mathematical formulation is given of the relative rates of incorporation of the new mutations with and without recombination. Recombination is of the greatest advantage when the double mutant is more advantageous than either single mutant, when the mutant effects are small, ...

Abstract

Presented here is a genome sequence of an individual human. It was produced from approximately 32 million random DNA fragments, sequenced by Sanger dideoxy technology and assembled into 4,528 scaffolds, comprising 2,810 million bases (Mb) of contiguous sequence with approximately 7.5-fold coverage for any given region. We developed a modified version of the Celera assembler to facilitate the identification and comparison of alternate alleles within this individual diploid genome. Comparison of this genome and the National Center for Biotechnology Information human ...

Abstract

DNA sequence information underpins genetic research, enabling discoveries of important biological or medical benefit. Sequencing projects have traditionally used long (400-800 base pair) reads, but the existence of reference sequences for the human and many other genomes makes it possible to develop new, fast approaches to re-sequencing, whereby shorter reads are compared to a reference to identify intraspecies genetic variation. Here we report an approach that generates several billion bases of accurate nucleotide sequence per experiment at low cost. Single molecules ...

Abstract

The association of genetic variation with disease and drug response, and improvements in nucleic acid technologies, have given great optimism for the impact of 'genomic medicine'. However, the formidable size of the diploid human genome, approximately 6 gigabases, has prevented the routine application of sequencing methods to deciphering complete individual human genomes. To realize the full potential of genomics for human health, this limitation must be overcome. Here we report the DNA sequence of a diploid genome of a single individual, ...

Abstract

The vernalization gene VRN-1 has been identified as a MADS-box transcription factor orthologous to the meristem identity gene APETALA1 (AP1). A single copy of this gene was found in diploid wheat, but 2 copies were reported in barley. In this study, we present a detailed characterization of these 2 copies to understand their respective roles in the vernalization response. We identified 2 groups of barley bacterial artificial chromosomes (BACs), each containing 1 AP1 copy designated hereafter as HvAP1a and HvAP1b. A ...

Note (first note only)

Times Cited: 2 Cited Reference Count: 21 Cited References: DANYLUK J, 2003, PLANT PHYSIOL, V132, P1849 DUBCOVSKY J, 1995, P NATL ACAD SCI USA, V92, P6645 DUBCOVSKY J, 1996, GENETICS, V143, P983 DUBCOVSKY J, 1998, THEOR APPL GENET, V97, P968 DUBCOVSKY J, 2001, PLANT PHYSIOL, V125, P1342 DUBCOVSKY J, 2005, MOL BREEDING, V15, P395 FRANCKOWIAK JD, 1997, BARLEY GENET NEWSL, V26, P212 FU DL, 2005, MOL GENET GENOMICS, V273, P54 HAYES PM, 1997, PLANT COLD HARDINESS, P77 LAURIE DA, 1995, GENOME, V38, P575 RAMAKRISHNA W, 2002, GENETICS, V162, P1389 SCHMITZ J, 2000, PLANT MOL BIOL,

Abstract

Variation analyses in the human genome at the sequence level, especially human genetic population analysis and genetic epidemiology, are hampered by the difficulty to ascertain haplotypes on autosomal regions. We have designed a new methodological approach to obtain autosomal haploid sequences from diploid organisms. First, genotypes are unambiguously determined through long-range PCR and diploid DNA sequencing. Second, cloning the whole PCR-amplified segment and sequencing a single clone for those fragments that presented a heterozygous position discern the allelic phase. The second ...

Note (first note only)

Times Cited: 4 Cited Reference Count: 9 Cited References: CLARK AG, 1990, MOL BIOL EVOL, V7, P111 CLARK AG, 1998, AM J HUM GENET, V63, P595 FULLERTON SM, 2000, AM J HUM GENET, V67, P881 HARDING RM, 1997, AM J HUM GENET, V60, P772 JANSEN R, 1990, NUCLEIC ACIDS RES, V18, P5153 JIN L, 1999, P NATL ACAD SCI USA, V96, P3796 MARTINEZARIAS R, 2001, GENOME RES, V11, P1071 NICKERSON DA, 1997, NUCLEIC ACIDS RES, V25, P2745 SHIMMIN LC, 1998, MOL BIOL EVOL, V15, P449 English Article DNA SEQUENCE 559CW

Abstract

Painting of fourth (POF) is a chromosome-specific protein in Drosophila and represents the first example of an autosome-specific protein. POF binds to chromosome 4 in Drosophila melanograster, initiating at the proximal region, followed by a spreading dependent on chromosome 4-specific sequences or structures. Chromosome-specific gene regulation is known thus far only as a mechanism to equalize the transcriptional activity of the single male X chromosome with that of the two female X chromosomes. In Drosophila, a complex including the male-specific lethal ...

Note (first note only)

Times Cited: 6 Cited Reference Count: 45 Cited References: AKHTAR A, 2003, CURR OPIN GENET DEV, V13, P161 ASHBURNER M, 1989, DROSOPHILA LAB HDB BARIGOZZI C, 1966, EXP CELL RES, V43, P231 BEALL EL, 1996, GENE DEV, V10, P921 BONE JR, 1996, GENETICS, V144, P705 BONVICINO CR, 2003, FOLIA PRIMATOL, V74, P141 BRAND AH, 1994, METHOD CELL BIOL, V44, P635 CZERMIN B, 2002, CELL, V111, P185 EISSENBERG JC, 1992, GENETICS, V131, P345 FRANKE A, 1999, MOL CELL, V4, P117 GANESAN S, 2002, CELL, V111, P393 GLOOR GB, 1993, GENETICS, V135, P81 HALL TA, 1999, NUCL ACIDS

Abstract

In species with single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. In the haplodiploid Hymenoptera, sl-CSD results in females, if individuals are heterozygous at the sex locus, and in males, if individuals are hemizygous (haploid males) or homozygous (diploid males). Several hymenopteran species have been shown to have sl-CSD, but in several others sl-CSD is absent and the phylogenetic distribution remains unclear. In the family Braconidae, all four species tested so far were shown ...

Note (first note only)

Times Cited: 17 Cited Reference Count: 39 Cited References: ANTOLIN MF, 1992, ECOL ENTOMOL, V17, P1 BEUKEBOOM LW, 1995, BIOESSAYS, V17, P813 BULL JJ, 1983, EVOLUTION SEX DETERM BUTCHER RDJ, 1998, P 6 EUR C ENT CESK B, P161 CLARK AM, 1961, RADIAT RES, V15, P244 COOK JM, 1993, HEREDITY, V71, P130 COOK JM, 1993, HEREDITY, V71, P421 COOK JM, 1995, TRENDS ECOL EVOL, V10, P281 CROZIER RH, 1971, AM NAT, V105, P399 CROZIER RH, 1975, ANIMAL CYTOGENETICS, V3, P1 CROZIER RH, 1977, ANNU REV ENTOMOL, V22, P263 DUBENDORFER A, 1992, SEMIN DEV BIOL, V3,

Abstract

Genomes vary dramatically in size and in content. This variation is driven in part by numerous polyploidization events that have happened over the course of eukaryotic evolution. Experimental evolution studies, primarily using the yeast Saccharomyces cerevisiae, provide insights into the immediate fitness effects of ploidy mutations, the ability of organisms of different ploidy levels to mask deleterious mutations, the impact of ploidy on rates of adaptation, and the relative roles of selection versus drift in shaping ploidy evolution. We review these ...

Abstract

Explanations of the evolution of diploidy have focused on the advantages gained from masking deleterious alleles. Recent theory has shown, however, that masking does not always provide an advantage to diploidy and would never favor diploidy in predominantly asexual organisms. We explore a neglected alternative theory which posits that, by doubling the genome size, diploids double the rate at which favorable mutations arise. Consequently, the rate of adaptation in diploids is presumed to be faster than in haploids. The rate of ...

Abstract

The life cycle of eukaryotic, sexual species is divided into haploid and diploid phases. In multicellular animals and seed plants, the diploid phase is dominant, and the haploid phase is reduced to one, or a very few cells, which are dependent on the diploid form. In other eukaryotic species, however, the haploid phase may dominate or the phases may be equally developed. Even though an alternation between haploid and diploid forms is fundamental to sexual reproduction in eukaryotes, relatively little is ...

Abstract

Fixation processes in evolutionary game dynamics in finite diploid populations are investigated. Traditionally, frequency dependent evolutionary dynamics is modeled as deterministic replicator dynamics. This implies that the infinite size of the population is assumed implicitly. In nature, however, population sizes are finite. Recently, stochastic processes in finite populations have been introduced in order to study finite size effects in evolutionary game dynamics. One of the most significant studies on evolutionary dynamics in finite populations was carried out by Nowak et al. ...

Abstract

We consider the Wright Fisher model for a finite population of diploid sexual organisms where selection acts at a locus with multiple alleles. The mathematical description of a such a model requires vectors and matrices of a multidimensional nature, and hence has a considerable level of complexity. In the present work we avoid this complexity by introducing a simple mathematical transformation. This yields a description of the model in terms of ordinary vectors and ordinary matrices, thereby allowing standard linear algebra ...

Abstract

DNA sequence information underpins genetic research, enabling discoveries of important biological or medical benefit. Sequencing projects have traditionally used long (400–800 base pair) reads, but the existence of reference sequences for the human and many other genomes makes it possible to develop new, fast approaches to re-sequencing, whereby shorter reads are compared to a reference to identify intraspecies genetic variation. Here we report an approach that generates several billion bases of accurate nucleotide sequence per experiment at low cost. Single molecules of DNA are attached ...

Abstract

The probability of fixation of an overdominant mutation in a finite population depends on the equilibrium gene frequency in an infinite population (m) and the product (A) of population size and selection intensity. If m < 0.5 (disadvantageous overdominant genes), the probability is generally much lower than that of neutral genes; but if m is close to 0.5 and A is relatively small, it becomes higher. If m > 0.5 (advantageous overdominant genes), the probability is largely determined by the fitness ...

Abstract

The concept of the Evolutionarily Stable Strategy, or ESS, was originally formulated in terms of an effectively parthenogenetic population, a formulation which simplified the analysis but restricted the apparent applicability of the concept. In this note, the concept is shown to be consistent with the assumption of a sexual diploid population. ...

Abstract

Certain strains of Saccharomyces cerevisiae contain visible segments of synaptonemal complex which are apparent components of bivalents in pachytene of meiotic prophase. The synaptonemal complex has the typical width in the frontal plane but is unusually thin in the sagittal plane, thus accounting for its poor visibility. Amorphous densities situated adjacent to the central element occur at intervals suggesting their coincidence with sites of crossing over. Reconstruction of the synaptonemal complex from serial sections has permitted karyotypic analysis. The number of ...

Abstract

General frequency-dependent selection models based on two phenotypic classes are analyzed with underlying one-locus multiallele phenotypic determination systems in diploid populations. It is proved that the mean phenotypic fitnesses tend to equality over discrete generations and genetic mutations if a phenotypic polymorphism is to be maintained. The exact conditions are examined. The present results are valid for a wide class of models whenever random groupings or assortative patterns based on phenotype and affecting fitness, linearly or not, are independent of sex, ...

Abstract

We have investigated, numerically and analytically, long-term evolution under frequency-dependent disruptive selection of a continuous trait varying in a finite range and controlled by one diploid mendelian locus. We found that evolution converges towards a unique long-term equilibrium where only two extreme phenotypes are present with frequencies identical to those of the mixed strategy that would be the unique ESS of the game defined by the basic fitness function of the model. As long as this precise phenotypic composition is preserved, ...

Abstract

To a first order of approximation, selection is frequency independent in a wide range of family structured models and in populations following an island model of dispersal, provided the number of families or demes is large and the population is haploid or diploid but allelic effects on phenotype are semidominant. This result underlies the way the evolutionary stability of traits is computed in games with continuous strategy sets. In this paper similar results are derived under isolation by distance. The first-order ...

Abstract

For mixed strategies in finite populations, long-term stability is defined with respect to the probability of fixation of a mutant. Under weak selection, necessary and sufficient conditions are obtained using a diffusion approximation of the Wright–Fisher model or exact solutions for the Moran model. These differ from the usual ESS conditions if the strategies affect fertility instead of viability, leading to a game matrix depending on the population size, or if the mutant mixed strategy uses a new pure strategy. In ...

Abstract

Game theory has been used by some authors to analyse evolutionary limits to the expression of aggression in theoretical haploid parthenogenetic species. Others have examined frequency dependent selection, of which aggression may be a case, by applying population genetic models to diploid species. A model is presented which attempts to combine these two approaches. Game theory is used to determine evolutionarily stable strategies and corresponding stable polymorphisms for a two-strategy game played by members of a diploid sexual species, when choice ...