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Cell Nov 2015Chemical cross-linking and DNA sequencing have revealed regions of intra-chromosomal interaction, referred to as topologically associating domains (TADs), interspersed...
Chemical cross-linking and DNA sequencing have revealed regions of intra-chromosomal interaction, referred to as topologically associating domains (TADs), interspersed with regions of little or no interaction, in interphase nuclei. We find that TADs and the regions between them correspond with the bands and interbands of polytene chromosomes of Drosophila. We further establish the conservation of TADs between polytene and diploid cells of Drosophila. From direct measurements on light micrographs of polytene chromosomes, we then deduce the states of chromatin folding in the diploid cell nucleus. Two states of folding, fully extended fibers containing regulatory regions and promoters, and fibers condensed up to 10-fold containing coding regions of active genes, constitute the euchromatin of the nuclear interior. Chromatin fibers condensed up to 30-fold, containing coding regions of inactive genes, represent the heterochromatin of the nuclear periphery. A convergence of molecular analysis with direct observation thus reveals the architecture of interphase chromosomes.
Topics: Animals; Cell Nucleus; Chromosomal Puffs; Diploidy; Drosophila melanogaster; Genetic Techniques; Larva; Polytene Chromosomes
PubMed: 26544940
DOI: 10.1016/j.cell.2015.10.026 -
Genetics Dec 1980The meiotic effects of two cell-division-cycle mutations of Saccharomyces cerevisiae (cdc5 and cdc14) have been examined. These mutations were isolated by L.H. HARTWELL...
The meiotic effects of two cell-division-cycle mutations of Saccharomyces cerevisiae (cdc5 and cdc14) have been examined. These mutations were isolated by L.H. HARTWELL and his colleagues and characterized as defective in mitosis, causing a temperature-sensitive arrest in late nuclear division. When subjected to the restrictive temperature in meiosis, diploid cells homozygous for either of these mutations generally proceeded through premeiotic DNA synthesis and commitment to meiotic levels of recombination, but then arrested at a stage following spindle pole body (SPB) duplication and separation. The two SPBs lacked the interconnection by spindle microtubules typical of the complete meiosis I spindle. Challenge of these homozygotes by a semi-restrictive temperature often caused the production of asci containing two diploid spores. Genetic analysis of the viable pairs of spores revealed that each spore had become homozygous for centromere-linked markers significantly more frequently than for distal markers, indicating that the two spores each contained pairs of sister centromeres that had co-segregated in the reductional division of meiosis I. Ultrastructural analysis of the cdc5 homozygote demonstrated that these cells had completed meiosis I and formed two meiosis II spindles, but that the latter remained unusually short. This resulted in the encapsulation of both poles of each spindle within a single spore wall. These mutations therefore are defective in both meiotic divisions, as well as in the mitotic division described originally.
Topics: Cell Cycle; DNA, Fungal; Diploidy; Meiosis; Microscopy, Electron; Mutation; Phenotype; Recombination, Genetic; Saccharomyces cerevisiae; Spores, Fungal
PubMed: 7021319
DOI: 10.1093/genetics/96.4.859 -
Fertility and Sterility Sep 2009To review data on the microsurgical removal of a single pronucleus from tripronuclear human oocytes and evaluate the future potential of this technique for obtaining... (Review)
Review
OBJECTIVE
To review data on the microsurgical removal of a single pronucleus from tripronuclear human oocytes and evaluate the future potential of this technique for obtaining diploid, transferable embryos.
DESIGN
Literature review.
SETTING
None.
PATIENT(S)
None.
INTERVENTION(S)
None.
MAIN OUTCOME MEASURE(S)
None.
RESULT(S)
Ten relevant studies were identified. These differ considering the removal technique itself, the application of cytoskeletal relaxants, and the survival rate after epronucleation. Diploidy and heteroparental inheritances could be confirmed in some preimplantation stages derived from epronucleated oocytes. Transfer of "corrected" embryos has been attempted only once, and resulted in a live birth. Noteworthy pitfalls associated with the procedure concern the exact identification of the supernumerary pronucleus, the presence of two centrosomes in dispermic oocytes, and cytogenetically abnormal pronuclear patterns after intracytoplasmic sperm injection.
CONCLUSION(S)
Patients with exclusively abnormally or few normally fertilized oocytes would profit from epronucleation to assure embryo transfer or increase the number of transferable embryos. Further research appears necessary and promising.
Topics: Cell Nucleus; Centrosome; Diploidy; Embryo Transfer; Female; Fertilization in Vitro; Humans; Male; Microsurgery; Sperm Injections, Intracytoplasmic
PubMed: 18774562
DOI: 10.1016/j.fertnstert.2008.07.1740 -
The International Journal of... 2005We studied the developmental potential of single blastomeres from early cleavage mouse embryos. Eight- and sixteen-cell diploid mouse embryos were disaggregated and...
We studied the developmental potential of single blastomeres from early cleavage mouse embryos. Eight- and sixteen-cell diploid mouse embryos were disaggregated and single blastomeres from eight-cell embryos or pairs of sister blastomeres from sixteen-cell embryos were aggregated with 4, 5 or 6 tetraploid blastomeres from 4-cell embryos. Each diploid donor embryo gave eight sister aggregates, which later were manipulated together as one group (set). The aggregates were cultured in vitro until the blastocyst stage, when they were transferred (in sets) to the oviducts of pseudopregnant recipients. Eighteen live foetuses or pups were obtained from the transfer (11.0% of transferred blastocysts) and out of those, eleven developed into fertile adults (one triplet, one pair of twins and four singletons). In all surviving adults, pups and living foetuses, only diploid cells were detected in their organs and tissues as shown by analysis of coat pigmentation and distribution of glucose phosphate isomerase isoforms. In order to explain the observed high rate of mortality of transferred blastocysts, in an accompanying experiment, the diploid and tetraploid blastomeres were labelled with different fluorochromes and then aggregated. These experiments showed the diploid cells to be present not only in the inner cell mass (ICM) but also in the trophectoderm. The low number of diploid cells and the predominance of tetraploid cells in the ICM of chimaeric blastocysts might have been responsible for high postimplantation mortality of our experimental embryos.
Topics: Animals; Animals, Newborn; Blastomeres; Cell Survival; Chimera; Diploidy; Embryonic Development; Female; Fetus; Litter Size; Male; Mice; Polyploidy; Twins
PubMed: 16172978
DOI: 10.1387/ijdb.052018at -
International Journal of Molecular... Jul 2022Sexual vs. asexual reproduction-unisexual vs. bisexual populations-diploid vs. polyploid biotypes-genetic vs. environmental sex determination: all these natural... (Review)
Review
Sexual vs. asexual reproduction-unisexual vs. bisexual populations-diploid vs. polyploid biotypes-genetic vs. environmental sex determination: all these natural phenomena are associated with the genus of teleost fish, . This review places emphasis on two entities with completely different biological characteristics: one globally widespread and invasive , and the other with a decreasing trend of natural occurrence. Comprehensive biological and cytogenetic knowledge of both entities, including the physical interactions between them, can help to balance the advantages of highly invasive and disadvantages of threatened species. For example, the benefits of a wide-ranged colonization can lead to the extinction of native species or be compensated by parasitic enemies and lead to equilibrium. This review emphasizes the comprehensive biology and cytogenetic knowledge and the importance of the genus as one of the most useful experimental vertebrate models for evolutionary biology and genetics. Secondly, the review points out that effective molecular cytogenetics should be used for the identification of various species, ploidy levels, and hybrids. The proposed investigation of these hallmark characteristics in may be applied in conservation efforts to sustain threatened populations in their native ranges. Furthermore, the review focuses on the consequences of the co-occurrence of native and non-native species and outlines future perspectives of research.
Topics: Animals; Cyprinidae; Cytogenetic Analysis; Cytogenetics; Diploidy; Ploidies
PubMed: 35897665
DOI: 10.3390/ijms23158095 -
Heredity Jun 2021Inferring the demographic history of species is one of the greatest challenges in populations genetics. This history is often represented as a history of size changes,...
Inferring the demographic history of species is one of the greatest challenges in populations genetics. This history is often represented as a history of size changes, ignoring population structure. Alternatively, when structure is assumed, it is defined a priori as a population tree and not inferred. Here we propose a framework based on the IICR (Inverse Instantaneous Coalescence Rate). The IICR can be estimated for a single diploid individual using the PSMC method of Li and Durbin (2011). For an isolated panmictic population, the IICR matches the population size history, and this is how the PSMC outputs are generally interpreted. However, it is increasingly acknowledged that the IICR is a function of the demographic model and sampling scheme with limited connection to population size changes. Our method fits observed IICR curves of diploid individuals with IICR curves obtained under piecewise stationary symmetrical island models. In our models we assume a fixed number of time periods during which gene flow is constant, but gene flow is allowed to change between time periods. We infer the number of islands, their sizes, the periods at which connectivity changes and the corresponding rates of connectivity. Validation with simulated data showed that the method can accurately recover most of the scenario parameters. Our application to a set of five human PSMCs yielded demographic histories that are in agreement with previous studies using similar methods and with recent research suggesting ancient human structure. They are in contrast with the view of human evolution consisting of one ancestral population branching into three large continental and panmictic populations with varying degrees of connectivity and no population structure within each continent.
Topics: Diploidy; Gene Flow; Genetics, Population; Humans; Population Density
PubMed: 33846579
DOI: 10.1038/s41437-021-00426-9 -
Laboratory Animals Aug 2023Information about the diploid genotype of a gene-modified or mutant laboratory animal is essential for breeding and experimental planning. It is also required for the...
Information about the diploid genotype of a gene-modified or mutant laboratory animal is essential for breeding and experimental planning. It is also required for the exchange of animals between different research groups or for communication with professional genotyping service providers. While there are detailed, standardized rules for creating an allele name of a genome modification or mutation, the notation of the diploid genotype after biopsy and genotyping has not been standardized yet. Therefore, a uniform, generally understandable nomenclature for the diploid genotype of gene-modified laboratory animals is needed. With the here-proposed nomenclature recommendations from the Committee on Genetics and Breeding of Laboratory Animals of the German Society for Laboratory Animal Science (GV-SOLAS), we provide a practical, standardized representation of the genotype of gene-modified animals. It is intended to serve as a compact guide for animal care and scientific personnel in animal research facilities and to simplify data exchange between groups and with external service providers.
Topics: Animals; Diploidy; Genotype; Animal Husbandry; Laboratory Animal Science
PubMed: 37672033
DOI: 10.1177/00236772231175727 -
Annals of Botany May 2020Pollen tube growth rate (PTGR) is an important single-cell performance trait that may evolve rapidly under haploid selection. Angiosperms have experienced repeated...
BACKGROUND AND AIMS
Pollen tube growth rate (PTGR) is an important single-cell performance trait that may evolve rapidly under haploid selection. Angiosperms have experienced repeated cycles of polyploidy (whole genome duplication), and polyploidy has cell-level phenotypic consequences arising from increased bulk DNA amount and numbers of genes and their interactions. We sought to understand potential effects of polyploidy on several underlying determinants of PTGR - pollen tube dimensions and construction rates - by comparing diploid-polyploid near-relatives in Betula (Betulaceae) and Handroanthus (Bignoniaceae).
METHODS
We performed intraspecific, outcrossed hand-pollinations on pairs of flowers. In one flower, PTGR was calculated from the longest pollen tube per time of tube elongation. In the other, styles were embedded in glycol methacrylate, serial-sectioned in transverse orientation, stained and viewed at 1000× to measure tube wall thicknesses (W) and circumferences (C). Volumetric growth rate (VGR) and wall production rate (WPR) were then calculated for each tube by multiplying cross-sectional tube area (πr2) or wall area (W × C), by the mean PTGR of each maternal replicate respectively.
KEY RESULTS
In Betula and Handroanthus, the hexaploid species had significantly wider pollen tubes (13 and 25 %, respectively) and significantly higher WPRs (22 and 18 %, respectively) than their diploid congeners. PTGRs were not significantly different in both pairs, even though wider polyploid tubes were predicted to decrease PTGRs by 16 and 20 %, respectively.
CONCLUSIONS
The larger tube sizes of polyploids imposed a substantial materials cost on PTGR, but polyploids also exhibited higher VGRs and WPRs, probably reflecting the evolution of increased metabolic activity. Recurrent cycles of polyploidy followed by genome reorganization may have been important for the evolution of fast PTGRs in angiosperms, involving a complex interplay between correlated changes in ploidy level, genome size, cell size and pollen tube energetics.
Topics: Cross-Sectional Studies; Diploidy; Humans; Magnoliopsida; Pollen Tube; Polyploidy
PubMed: 31957784
DOI: 10.1093/aob/mcaa007 -
Theoretical Population Biology Jun 2021Recent modeling studies interested in runs of homozygosity (ROH) and identity by descent (IBD) have sought to connect these properties of genomic sharing to pairwise...
Recent modeling studies interested in runs of homozygosity (ROH) and identity by descent (IBD) have sought to connect these properties of genomic sharing to pairwise coalescence times. Here, we examine a variety of features of pairwise coalescence times in models that consider consanguinity. In particular, we extend a recent diploid analysis of mean coalescence times for lineage pairs within and between individuals in a consanguineous population to derive the variance of coalescence times, studying its dependence on the frequency of consanguinity and the kinship coefficient of consanguineous relationships. We also introduce a separation-of-time-scales approach that treats consanguinity models analogously to mathematically similar phenomena such as partial selfing, using this approach to obtain coalescence-time distributions. This approach shows that the consanguinity model behaves similarly to a standard coalescent, scaling population size by a factor 1-3c, where c represents the kinship coefficient of a randomly chosen mating pair. It provides the explanation for an earlier result describing mean coalescence time in the consanguinity model in terms of c. The results extend the potential to make predictions about ROH and IBD in relation to demographic parameters of diploid populations.
Topics: Consanguinity; Diploidy; Homozygote; Humans; Population Density
PubMed: 33675872
DOI: 10.1016/j.tpb.2021.02.002 -
ELife Oct 2021Evolutionary adaptation to a constant environment is driven by the accumulation of mutations which can have a range of unrealized pleiotropic effects in other...
Evolutionary adaptation to a constant environment is driven by the accumulation of mutations which can have a range of unrealized pleiotropic effects in other environments. These pleiotropic consequences of adaptation can influence the emergence of specialists or generalists, and are critical for evolution in temporally or spatially fluctuating environments. While many experiments have examined the pleiotropic effects of adaptation at a snapshot in time, very few have observed the dynamics by which these effects emerge and evolve. Here, we propagated hundreds of diploid and haploid laboratory budding yeast populations in each of three environments, and then assayed their fitness in multiple environments over 1000 generations of evolution. We find that replicate populations evolved in the same condition share common patterns of pleiotropic effects across other environments, which emerge within the first several hundred generations of evolution. However, we also find dynamic and environment-specific variability within these trends: variability in pleiotropic effects tends to increase over time, with the extent of variability depending on the evolution environment. These results suggest shifting and overlapping contributions of chance and contingency to the pleiotropic effects of adaptation, which could influence evolutionary trajectories in complex environments that fluctuate across space and time.
Topics: Acclimatization; Adaptation, Biological; Diploidy; Environment; Genetic Fitness; Genetic Pleiotropy; Haploidy; Saccharomyces cerevisiae
PubMed: 34596043
DOI: 10.7554/eLife.70918