Search results for "Diploidy"

Chemotactic migration of human diploid fibroblasts is inhibited by contactinhibin.

1992

Sex Allocation in Haplodiploid Cyclical Parthenogens with Density‐Dependent Proportion of Males

1998

Departament de Microbiologia i Ecologia, Universitat de Birky and Gilbert 1971; Wallace and Snell 1991), which Valencia, E46100-Burjassot (Valencia), Spain includes an asexual (amictic) and a sexual (mictic) phase, the diapausing form being the sexually produced resting Submitted September 22, 1997; Accepted April 21, 1998 egg. Habitat colonization begins when the resting eggs hatch and emerge from the sediments. With these hatchlings, the amictic phase starts, which is a repeated sequence of amictic females parthenogenetically produc

Past climate changes facilitated homoploid speciation in three mountain spiny fescues (Festuca, Poaceae)

2016

Apart from the overwhelming cases of allopolyploidization, the impact of speciation through homoploid hybridization is becoming more relevant than previously thought. Much less is known, however, about the impact of climate changes as a driven factor of speciation. To investigate these issues, we selected Festuca picoeuropeana, an hypothetical natural hybrid between the diploid species F. eskia and F. gautieri that occurs in two different mountain ranges (Cantabrian Mountains and Pyrenees) separated by more than 400 km. To unravel the outcomes of this mode of speciation and the impact of climate during speciation we used a multidisciplinary approach combining genome size and chromosome coun…

Self-diploidization in Saccharomyces cerevisiae kar2 heterokaryons

1993

Zygotes isolated by micromanipulation from crosses of Saccharomyces cerevisiae strains, one of which carries a kar mutation, give rise most frequently to cytoductant colonies showing the nuclear constitution of either one of the two haploid parental strains. In crosses of kar2-1 strains to wild-type, about 10% of the cytoductants of both mating types are homozygous autodiploids. There is evidence indicating that self-diploidization occurs by fusion between sibling nuclei in the heterokaryotic zygote. Here we describe this phenomenon and propose to take advantage of it for the construction of genotypically-defined diploids able to mate, and of polyploid strains, which are useful tools in gen…

No inbreeding depression but increased sexual investment in highly inbred ant colonies.

2012

Inbreeding can lead to the expression of deleterious recessive alleles and to a subsequent fitness reduction. In Hymenoptera, deleterious alleles are purged in haploid males moderating inbreeding costs. However, in these haplodiploid species, inbreeding can result in the production of sterile diploid males. We investigated the effects of inbreeding on the individual and colony level in field colonies of the highly inbred ant Hypoponera opacior. In this species, outbreeding winged sexuals and nest-mating wingless sexuals mate during two separate reproductive periods. We show that regular sib-matings lead to high levels of homozygosity and the occasional production of diploid males, which spo…

Intergenomic interactions affect female reproduction: evidence from introgression and inbreeding depression in a haplodiploid mite

2004

Nuclear and cytoplasmic genomes can coevolve antagonistically or harmoniously to affect fitness. One commonly used test for nuclear-cytoplasmic coadaptation relies on the breakup of coadapted gene complexes by introgression, potentially resulting in an increased frequency of nuclear alleles in deleterious interaction with an alien cytoplasm. We investigated the phenotypic effect of such genes on female reproduction in outbred and inbred introgressed lines of the haplodiploid mite Tetranychus urticae. Introgression changed female lifetime fecundity and increased male production, in ways suggesting a control of fecundity by nuclear genes. Conversely introgression reduced the fertilization rat…

Similar Performance of Diploid and Haploid Males in an Ant Species without Inbreeding Avoidance

2013

AbstractUnder haplodiploidy, a characteristic trait of all Hymenoptera, femalesdevelop from fertilised eggs, and males from unfertilised ones. Males aretherefore typically haploid. Yet, inbreeding can lead to the production ofdiploid males that often fail in development, are sterile or are of lowerfertility. In most Hymenoptera, inbreeding is avoided by dispersal flightsof one or both sexes, leading to low diploid male loads. We investigatedcauses for the production of diploid males and their performance in ahighly inbred social Hymenopteran species. In the ant Hypoponera opacior,inbreeding occurs between wingless sexuals, which mate within themother nest, whereas winged sexuals outbreed dur…

Checkpoint adaptation in recombination-deficient cells drives aneuploidy and resistance to genotoxic agents.

2020

Abstract Human cancers frequently harbour mutations in DNA repair genes, rendering the use of DNA damaging agents as an effective therapeutic intervention. As therapy-resistant cells often arise, it is important to better understand the molecular pathways that drive resistance in order to facilitate the eventual targeting of such processes. We employ recombination-defective diploid yeast as a model to demonstrate that, in response to genotoxic challenges, nearly all cells eventually undergo checkpoint adaptation, resulting in the generation of aneuploid cells with whole chromosome losses that have acquired resistance to the initial genotoxic challenge. We demonstrate that adaptation inhibit…

Mapping genomic rearrangements in titi monkeys by chromosome flow sorting and multidirectional in-situ hybridization.

2004

We developed chromosome painting probes for Callicebus pallescens from flow-sorted chromosomes and used multidirectional chromosome painting to investigate the genomic rearrangements in C. cupreus and C. pallescens. Multidirectional painting provides information about chromosomal homologies at the subchromosomal level and rearrangement break points, allowing chromosomes to be used as cladistic markers. Chromosome paints of C. pallescens were hybridized to human metaphases and 43 signals were detected. Then, both human and C. pallescens probes were hybridized to the chromosomes of another titi monkey, C. cupreus. The human chromosome paints detected 45 segments in the haploid karyotype of C.…

Large variation in mitochondrial DNA of sexual and parthenogenetic Dahlica triquetrella (Lepidoptera: Psychidae) shows multiple origins of parthenoge…

2013

Background Obligate parthenogenesis is relatively rare in animals. Still, in some groups it is quite common and has evolved and persisted multiple times. These groups may provide important clues to help solve the ‘paradox of sex’. Several species in the Psychidae (Lepidoptera) have obligate parthenogenesis. Dahlica triquetrella is one of those species where multiple transitions to parthenogenesis are postulated based on intensive cytological and behavioural studies. This has led to the hypothesis that multiple transitions from sexuals to diploid parthenogens occurred during and after the last glacial period, followed by transitions from parthenogenetic diploids to parthenogenetic tetraploid…