• Objectives: To determine the sensitivity and specificity of combining fluorescence in situ hybridization (FISH) measurement of chromosome 9 and DNA cytometry of bladder irrigation specimens in the detection of bladder cancer. (johnshopkins.edu)
  • During her training in Japan, Dr. Burdo mastered the FISH (Fluorescence In Situ Hybridization) technique for analyzing chromosome aberrations in mice. (go.jp)
  • In order to assess the neoplastic nature of the lesion, we performed fluorescence in-situ hybridization (FISH) analysis using a probe which maps to the chromosome band 22q11 and 22q13, allowing us to show deletion or loss of one chromosome 22 in the tumour cells. (nih.gov)
  • Materials and Methods: To investigate both the presence of numerical abnormalities of chromosome 9 and p16 gene alterations in ovarian cancer, we studied 28 cases by the fluorescence in situ hybridization (FISH) technique using a DNA p16 probe and an a-satellite probe specific for chromosome 9. (iiarjournals.org)
  • The aim of the present study was to determine the significance of this tumor suppressor gene for ovarian tumorigenesis, investigating both numerical aberrations of chromosome 9 and p16 gene alterations in 28 cases of ovarian tumors, by the fluorescence in situ hybridization (FISH) technique. (iiarjournals.org)
  • Fluorescence in situ hybridization, spectral karyotyping, multiplex fluorescence in situ hybridization, comparative genomic hybridization, and more recently array comparative genomic hybridization, represent advancements in the field of molecular cytogenetics. (elsevierpure.com)
  • Based on conventional cytogenetic analysis of banded chromosomes, we selected a series of 23 paediatric patients with acute myeloid leukaemia and performed whole genome array comparative genome hybridization (aCGH) using DNA samples derived from the same patients. (ox.ac.uk)
  • Results were validated by fluorescence in situ hybridization (FISH) to both interphase nuclei and metaphase chromosomes using appropriate bacterial artificial chromosome (BAC) probes. (ox.ac.uk)
  • Chromosome analysis was performed on 47-h cultures using single-color fluorescence in situ hybridization (FISH) to paint chromosomes 1, 3 and 5. (bioone.org)
  • This includes both karyotyping of banded chromosomes and, since the nineties of the last century, also fluorescence in situ hybridization (FISH). (biomedcentral.com)
  • Translocations were scored in an average of 1039 cell equivalents (CE) per subject using fluorescence in situ hybridization with whole chromosome paints, and expressed per 100 CE. (cdc.gov)
  • In this study, paraffin-embedded material of five cases of pleuropulmonary blastoma was analyzed for genetic alterations by comparative genomic hybridization and five genetic loci by fluorescence in situ hybridization. (prinsesmaximacentrum.nl)
  • Comparative genomic hybridization identified aberrations in all pleuropulmonary blastomas, including four amplifications in three tumors at chromosomes 5q33-34, 11q22.2-ter, 15q25-ter, and 19q11-13.2. (prinsesmaximacentrum.nl)
  • Chromosome 8 gains were confirmed by fluorescent in situ hybridization, resulting in the detection of up to five copies of chromosome 8 centromeres per nucleus. (prinsesmaximacentrum.nl)
  • To evaluate the technical and clinical feasibility of next-generation sequencing on cfDNA for detecting leukemic clonal abnormalities, a pilot study was performed on ten residual samples to compare results from cfDNA sequencing analysis (cfDSA) with diagnostic findings from karyotyping, fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH). (najms.com)
  • Fluorescence in situ hybridization (FISH) is a robust technique of cytogenetic used for the detection of chromosomal aberrations, presence or absence of specific DNA sequence in native context. (biogenex.com)
  • Second, fluorescence in situ hybridization was conducted for the region containing the HMGA2 gene in addition to expression analysis, to study the recurrence of changes at this locus. (annexpublishers.co)
  • Thirty-four cases of CLL were screened for the 11q23, 13q14, 17p13 deletions, and trisomy 12 by fluorescence in situ hybridization (FISH). (nebraska.edu)
  • Objectives: Polysomy detected by fluorescence in situ hybridization (FISH) is associated with cholangiocarcinoma (CCA) in patients with primary sclerosing cholangitis (PSC). (elsevierpure.com)
  • A short introduction how cytogenetics and molecular cytogenetics were established is followed by technical aspects of fluorescence in situ hybridization (FISH). (frontiersin.org)
  • This review is about "molecular cytogenetics" including 1) the historical perspective of its development from cytogenetics, 2) technical aspects, 3) available probe sets, and 4) variants and applications of the basic fluorescence in situ hybridization (FISH) approach. (frontiersin.org)
  • A customized sequencing and interpretation pipeline was developed to identify chromosomal rearrangements and deletions/duplications with confirmation by fluorescence in situ hybridization, chromosomal microarray analysis, and PCR studies. (ku.dk)
  • This technique may also be used to identify cross-species homology by labeling probes from one species for hybridization with chromosomes from another species. (uams.edu)
  • Pathak R, Koturbash I, Hauer-Jensen M. Detection of Inter-chromosomal Stable Aberrations by Multiple Fluorescence In Situ Hybridization (mFISH) and Spectral Karyotyping (SKY) in Irradiated Mice. (uams.edu)
  • Premature chromosome condensation in human resting peripheral blood lymphocytes without mitogen stimulation for chromosome aberration analysis using specific whole chromosome DNA hybridization probes. (uams.edu)
  • To address this issue, we used multicolor combined binary ratio fluorescence in situ hybridization (FISH), which allows the simultaneous visualization of all 24 chromosomes in different colors, verified by locus-specific FISH in a series of 33 CML cases. (lu.se)
  • Fluorescence "in situ" hybridization (FISH) technique enables chromosomes to be tagged with fluorescent dyes to highlight genetic traits. (lu.se)
  • L'hybridation fluorescente in situ (FISH) est une technique qui permet des séquences d'ADN spécifiques à détecter sur les chromosomes en métaphase ou en interphase en 1 noyaux des cellules. (jove.com)
  • Chromosomal painting of chromosomes 1 and 4 using the fluorescence in situ hybridisation technique was also applied to four subjects to assess the stable chromosome aberration. (bvsalud.org)
  • A more comprehensive analysis should be conducted in a subsequent study by increasing the number of study donors and the number of metaphases to be analysed in both dicentric chromosome assay and fluorescence in situ hybridisation assays. (bvsalud.org)
  • This advanced technique uses two or more fluorescent dyes to stain chromosomes in order to detect abnormalities. (go.jp)
  • Results: Numerical abnormalities of chromosome 9 were found in all studied cases. (iiarjournals.org)
  • Leukaemia is often associated with genetic alterations such as translocations, amplifications and deletions, and recurrent chromosome abnormalities are used as markers of diagnostic and prognostic relevance. (ox.ac.uk)
  • They underlie genetic disease in roughly 15% of patients with multiple congenital abnormalities and/or mental retardation (MCA/MR). In genetic diagnostics, the pathogenicity of chromosomal aberrations in these patients is typically assessed based on criteria such as phenotypic similarity to other patients with the same or overlapping aberration, absence in healthy individuals, de novo occurrence, and protein coding gene content. (biomedcentral.com)
  • Mosaic) aneuploidies and chromosomal rearrangements are a frequent cause of idiopathic MCA/MR. Starting in 1959 with the identification of trisomy-21 as the genetic basis of Down syndrome [ 10 ], microscopic observation of metaphase chromosomes has for several decades been the method of choice for detecting chromosome abnormalities in MCA/MR patients. (biomedcentral.com)
  • In patients with hematological malignancies, the cancerous cells undergoing apoptosis could release leukemic cfDNA into the blood plasma or bone marrow fluid, and the chromosomal profiling from those cfDNA could be used to detect clonal chromosome abnormalities. (najms.com)
  • In three samples with different clonal chromosome abnormalities, aCGH and cfDSA detected comparable copy number aberrations and further defined the chromosomal abnormalities. (najms.com)
  • The result from this pilot study demonstrated that leukemic cfDNA in the blood plasma, and possibly bone marrow fluid, could be used to detect clonal chromosome abnormalities. (najms.com)
  • Detection of four different 11q23 chromosomal abnormalities by multiplex-PCR and fluorescence-based automatic DNA-fragment analysis. (understandinginterventions.org)
  • Repp R, Borkhardt A, Haupt E, Kreuder J, Brettreich S, Hammermann J, Nishida K, Harbott J, Lampert F. Detection of four different 11q23 chromosomal abnormalities by multiplex-PCR and fluorescence-based automatic DNA-fragment analysis. (understandinginterventions.org)
  • Chromosome abnormalities influence prognosis and tumour progression in B-cell Chronic Lymphocytic Leukaemia (CLL). (nebraska.edu)
  • Expression of 205 cell signalling and apoptosis genes were compared by cDNA array among cases with different chromosome abnormalities. (nebraska.edu)
  • A strong overall correlation existed between the presence of different chromosome abnormalities and a number of prognostic factors including immunoglobulin heavy chain variable region mutation status (P = 0.011), time to treatment (P = 0.025) and lymphocyte doubling time (P = 0.034). (nebraska.edu)
  • This study confirmed the prognostic impact of chromosome abnormalities identified by FISH in CLL, particularly the 11q23 deletion and trisomy 12. (nebraska.edu)
  • In these couples, this protocol significantly increased the diagnostic yield of chromosomal abnormalities per couple (11.7%) in comparison to chromosome analysis (8.0%, chi-square test p = 0.000751). (ku.dk)
  • Antioxidant intake and chromosome translocation frequency among airline pilots. (cdc.gov)
  • During each of the two PCR rounds a sense primer located within exon 5 of the MLL gene at 11q23 was combined with four different antisense primers, each located within possible translocation partner genes at chromosomes 4, 6, 9, and 19, respectively. (understandinginterventions.org)
  • For this reason, automatic fluorescence-based DNA-fragment analysis was used to exactly define the MLL translocation partner genes if a positive result had been obtained by agarose gel analysis. (understandinginterventions.org)
  • In approximately half of translocation cases, a parent (usually the mother) has a balanced translocation, ie, 45 chromosomes with t(14;21). (medscape.com)
  • The remaining cases are due translocation, mosaicism and partial trisomy of the chromosome 21. (bvsalud.org)
  • Partial XCR may derepress one or more genes on the Xi, and the level of restored gene expression may not be as high as it would normally be on the active X chromosome (the Xa). (wikipedia.org)
  • In 1961, Mary Lyon proposed the random inactivation of one female X chromosome to explain the mottled phenotype of female mice heterozygous for coat color genes. (wikipedia.org)
  • To this end, we screen primary tumour material for pathogenetic aberrations using next-generation sequencing technology and we manipulate genes of interest in cancer model systems using the CRISPR/Cas9 gene editing system. (lu.se)
  • Genes, Chromosomes and Cancer. (lu.se)
  • Chromosome aberrations can affect one or more genes in a complex manner, such as by changing the regulation of gene expression, by disrupting exons, and by creating fusion genes. (biomedcentral.com)
  • Identifying genes on each chromosome is an active area of genetic research. (medlineplus.gov)
  • Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. (medlineplus.gov)
  • Chromosome 1 likely contains 2,000 to 2,100 genes that provide instructions for making proteins. (medlineplus.gov)
  • Researchers have identified several possible tumor suppressor genes in the deleted region of chromosome 1, and more research is needed to understand what role these genes play in neuroblastoma development. (medlineplus.gov)
  • In one case with FISH-detected deletions of 7q and 20q in 11-12% of cells, neither cfDSA nor aCGH detected any copy number aberrations. (najms.com)
  • In the following sections we first provide an overview of current methods for diagnostic detection and interpretation of chromosomal aberrations in MCA/MR patients. (biomedcentral.com)
  • HMGA2 is located in an area on chromosome 12q13 frequently involved in translocations and amplifications in benign, mesenchymal tumors. (annexpublishers.co)
  • Conclusion: Numerical aberrations of chromosome 9 and p16 gene deletion are common findings in ovarian cancer. (iiarjournals.org)
  • 1p36 deletion syndrome is caused by a deletion of genetic material from a specific region in the short (p) arm of chromosome 1. (medlineplus.gov)
  • Relevant of mutagenicity and clastogenici- angiosarcomas of the liver, which carcinogens discussed in this chap- ty, including the induction of sister are rare tumours, were identified in ter do not include pharmaceutical chromatid exchange (SCE), chro- humans, rats, and mice exposed to drugs classified in Group 1, which mosomal aberrations (CA), and mi- vinyl chloride. (who.int)
  • Humans normally have 46 chromosomes in each cell, divided into 23 pairs. (medlineplus.gov)
  • Therian female mammalian cells have two X chromosomes, while males have only one, requiring X-chromosome inactivation (XCI) for sex-chromosome dosage compensation. (wikipedia.org)
  • In eutherians, XCI is the random inactivation of one of the X chromosomes, silencing its expression. (wikipedia.org)
  • Complete XCR restores the Xi to Xa and erases the epigenetic memory of XCI, meaning that inducing X-inactivation again will randomly select an X chromosome to silence, rather than deterministically silencing the original Xi. (wikipedia.org)
  • This finding suggested, independently to two groups of investigators, that one of the X chromosomes underwent inactivation. (wikipedia.org)
  • In mice, Xi reactivation is known to occur in three developmental stages: In the oocyte after fertilization, the paternal X chromosome is reactivated, reversing male meiotic sex chromosome inactivation (MSCI). (wikipedia.org)
  • These data demonstrate the presence of cells in irrigation specimens with specific genomic lesions of chromosome 9 and DNA content. (johnshopkins.edu)
  • X chromosome reactivation (XCR) is the process by which the inactive X chromosome (the Xi) is re-activated in the cells of eutherian female mammals. (wikipedia.org)
  • The Lyon hypothesis also accounted for the findings that one copy of the X chromosome in female cells was highly condensed, and that mice with only one copy of the X chromosome developed as infertile females. (wikipedia.org)
  • This suggested to Ernest Beutler, studying heterozygous females for glucose-6-phosphate dehydrogenase (G6PD) deficiency, that there were two red cell populations of erythrocytes in such heterozygotes: deficient cells and normal cells, depending on whether the inactivated X chromosome (in the nucleus of the red cell's precursor cell) contains the normal or defective G6PD allele. (wikipedia.org)
  • In the case of low-dose exposure, more than 1,000 cells per mouse must be analyzed to detect chromosomal aberrations. (go.jp)
  • Consequently, this in vitro method can detect both structural and numerical chromosome aberrations in cells that have undergone cell division during or after exposure to the test chemical. (re-place.be)
  • Fluorescence and Giemsa banding studies of the allocyclic X chromosome in embryonic and adult mouse cells. (wikidata.org)
  • A more detailed analysis revealed that the majority of aberrations scored as dicentrics were part of complex/multiple aberrations, with the proportion of cells containing complexes increasing with dose. (bioone.org)
  • Cells containing aberrations involving painted chromosomes (FISH aberrations) were further classified according to cell stability and complexity. (bioone.org)
  • The majority of cells with FISH aberrations were unstable. (bioone.org)
  • The proportion of aberrant FISH cells with complex/multiple aberrations ranged from 56% at 10 mGy to 89% at 500 mGy. (bioone.org)
  • Here we describe a widely applicable nontoxic approach for measuring DNA content in live cells by fluorescence microscopy. (biomedcentral.com)
  • This method relies on introducing a live-cell membrane-permeant DNA fluorophore, such as Hoechst 33342, into the culture medium of cells at the end of any live-cell imaging experiment and measuring each cell's integrated nuclear fluorescence to quantify DNA content. (biomedcentral.com)
  • To overcome this limitation, approaches incorporating laser scanning cytometry and fluorescence microscopy have been successful in quantifying DNA content in single cells [ 2 , 3 ], providing the capacity to combine this information with additional cellular parameters that can be elucidated by imaging. (biomedcentral.com)
  • To overcome the limitations brought upon by cellular fixation, membrane-permeant DNA fluorophores were designed to stain DNA stoichiometrically in live-cells (supravital staining), enabling both the quantification of DNA content and the ability to track the movement of chromosomes over time. (biomedcentral.com)
  • chronic myeloid leukemia (cml) is characterized by increased and unregulated proliferation of granulocytic lineage in the bone marrow and presence of these immature myeloid cells in the peripheral blood with presence of philadelphia (ph) chromosome. (liverpool.ac.uk)
  • They described two patients with PNH with an acquired rearrangement of chromosome 12 affecting the HMGA2 gene, which encodes a chromatin remodeling protein, in the PIGA mutant cells [ 12 ]. (annexpublishers.co)
  • The main part deals with examples of modern FISH-applications, highlighting unique possibilities of the approach, like the possibility to study individual cells and even individual chromosomes. (frontiersin.org)
  • When such a gamete becomes fertilized, the fetus will have an extra chromosome 21 in all cells, for a total of 47 chromosomes. (medscape.com)
  • In another variant, mosaicism, some cells have 47 chromosomes and others have 46 because of an error in one of the first cell divisions of the fertilized egg. (medscape.com)
  • Chromosome 1 is the largest human chromosome, spanning about 249 million DNA building blocks (base pairs) and representing approximately 8 percent of the total DNA in cells. (medlineplus.gov)
  • Airline pilots are exposed to cosmic IR, an efficient inducer of chromosome aberrations (CA) which have been shown to be associated with increased cancer risk. (cdc.gov)
  • The image shows chromosomes from a cancer patient. (lu.se)
  • He has spent over 30 years studying various aspects of the changes to chromosomes that lead a cell to change and develop into a cancer cell, with a particular focus on leukaemia. (lu.se)
  • almost all tumours have chromosome changes and some are typical of different types of cancer. (lu.se)
  • Felix Mitelman's initiative of mapping all chromosome aberrations in cancer has helped to improve diagnosis, treatment and prognosis for different types of cancer. (lu.se)
  • Two copies of chromosome 1, one copy inherited from each parent, form one of the pairs. (medlineplus.gov)
  • The following chromosomal conditions are associated with changes in the structure or number of copies of chromosome 1. (medlineplus.gov)
  • A 1q21.1 microduplication is a copied (duplicated) segment of genetic material at position q21.1 on one of the two copies of chromosome 1 in each cell. (medlineplus.gov)
  • In 95% of cases, Down syndrome is caused by trisomy 21, in which the extra chromosome 21 in the egg or sperm cell results from the nondisjunction in the meiotic stage. (medscape.com)
  • Down Syndrome (DS) is the most common chromosomal aberration resulting from trisomy of the chromosome 21. (bvsalud.org)
  • Chromosome 9 copy number was determined on a cellular basis by FISH, and cellular DNA content was determined by Feulgen DNA staining and image cytometry. (johnshopkins.edu)
  • Results: Sensitivity of chromosome 9 FISH was 42% for all tumors and was not correlated to transitional cell carcinoma tumor grade, while the sensitivity of DNA cytometry was 55% and improved with increasing grade from 38% for grade 1 to 90% for grade 3 tumors. (johnshopkins.edu)
  • Conclusions: The lack of increase with grade in the percentage of positive specimens by FISH supports the hypothesis that chromosome 9 aberrations are critical events in bladder tumorigenesis for many patients. (johnshopkins.edu)
  • Combining FISH on chromosome 9 and DNA cytometry provides an in sensitivity to transitional cell carcinoma over either test alone. (johnshopkins.edu)
  • Mouse chromosomes stained using the FISH technique, viewed with a fluorescence microscope. (go.jp)
  • En règle générale, un test FISH unique examine seulement un ou quelques chromosomes entiersou des loci spécifiques par diapositive, etc hybridations multiples doivent être menées sur plusieurs diapositives pour couvrir l'ensemble des chromosomes humains. (jove.com)
  • Here especially highlighted variations of FISH are molecular combing, chromosome orientation-FISH (CO-FISH), telomere-FISH, parental origin determination FISH (POD-FISH), FISH to resolve the nuclear architecture, multicolor-FISH (mFISH) approaches, among other applied in chromoanagenesis studies, Comet-FISH, and CRISPR-mediated FISH-applications. (frontiersin.org)
  • Altogether, a refined karyotypic description was achieved in 12 (36%) of the 33 investigated cases, illustrating the value of using multicolor FISH for identifying pathogenetically important aberrations in CML AP/BC. (lu.se)
  • Chromosomes are elongated, coming from the nucleus (round, lower left). (lu.se)
  • For unstable chromosome aberration analysis, a dicentric chromosome assay was conducted using conventional Giemsa staining. (bvsalud.org)
  • Subsequently slides are mounted using DAPI/antifade and can be visualized under fluorescence microscope using appropriate filter set. (biogenex.com)
  • It was long believed that there were 48 chromosomes in total, but no one was sure because it was difficult to obtain good microscope slides. (lu.se)
  • In a control cohort of 68 human lymphocytes, telomere length and telomere aberrations were age-dependent and showed high inter-individual variation. (metasystems-probes.com)
  • Albert Levan, a researcher at Lund University, was the first to establish how many chromosomes there are in the human genome. (lu.se)
  • In the 1950s, Albert Levan and American Joe Hin Tjio improved the method, and in 1956 they established that the human genome is divided into 46 chromosomes, i.e. 23 pairs of chromosomes. (lu.se)
  • Micronuclei may originate from acentric chromosome fragments (i.e. lacking a centromere), or whole chromosomes that are unable to migrate to the poles during the anaphase stage of cell division. (re-place.be)
  • The frequencies of unstable and stable chromosome aberrations and micronuclei were examined in peripheral blood samples from 10 individuals living in elevated radon concentration areas (Takandeang Village, Mamuju, Indonesia). (bvsalud.org)
  • Since nuclear swelling (NS hereafter) has been frequently observed in chromosomal aberration (CA hereafter) tests (in vitro), the relationship between NS and CAs was investigated in this study. (biomedcentral.com)
  • POISSON OctoChrome est une technique prometteuse pour le diagnostic clinique de la leucémie et le lymphome et pour la détection d'aneuploïdies dans tous les chromosomes. (jove.com)
  • Our study showed no significant increases across all groups in dicentric and other unstable chromosome aberrations, such as rings and acentric fragments. (bvsalud.org)
  • Die beiden Structural Maintenance of Chromosomes (SMC)-Untereinheiten bilden zusammen mit einer Untereinheit aus der Familie der Kleisine eine dreigliedrige Ringstruktur aus, welche DNA-Stränge topologisch umschließen und dadurch intrachromosomale Verknüpfungen und Schlaufen stabilisieren kann. (uni-bayreuth.de)
  • The Precise Breakpoint Mapping in Paracentric Inversion 10q22.2q23.3 by Comprehensive Cytogenomic Analysis, Multicolor Banding, and Single-Copy Chromosome Sequencing. (metasystems-probes.com)
  • Multicolor banding, chromosomal microarray analysis, chromosome microdissection with reverse painting, and single-copy sequencing of the rearranged chromosome were performed to determine the length and position of the inverted region as well as to rule out a genetic imbalance at the breakpoints. (metasystems-probes.com)
  • As each of these techniques has advantages and limitations, a comprehensive analysis of cytogenetic aberrations can be accomplished through the utilization of a combination approach. (elsevierpure.com)
  • We performed low-pass GS retrospectively for 1,090 RM-affected couples, all of whom had routine chromosome analysis. (ku.dk)
  • As such, analyses of specific tumor types have proven invaluable in the identification of new tumor-specific chromosomal aberrations and imbalances (aneuploidy), as well as regions containing tumor-specific gene targets. (elsevierpure.com)
  • The karyotype demonstrated tumor cell patterns with aneuploidy and complex chromosomal aberrations. (biomedcentral.com)
  • The whole genome was analyzed for unstable aberrations to derive aberration frequencies and determine cell stability. (bioone.org)
  • Chromosome Painting" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (uams.edu)
  • In spite of the clear association between large ( de novo ) CNVs and other SVs (collectively known as chromosomal aberrations) with MCA/MR phenotypes [ 9 ], precise characterization of molecular mechanisms that cause disease in individual patients is often unknown. (biomedcentral.com)
  • Possible approaches for cytogenomic assessment of couples with balanced chromosome rearrangements and problems like reproductive failures were considered and suggested as useful part of effective genetic counseling. (metasystems-probes.com)
  • Imbalances involving large chromosomal regions or entire chromosomes were detected by aCGH in seven of the patients studied. (ox.ac.uk)
  • In the two surviving patients, chromosome 8 gains were the only genetic abnormality, suggesting that this might be an early event in pleuropulmonary blastoma carcinogenesis. (prinsesmaximacentrum.nl)
  • j) Annexes A to F containing sample instructions for the customer, sample questionnaire, sample datasheet for recording aberrations, sample of report and fitting of the low dose-response curve by the method of maximum likelihood and calculating the uncertainty of dose estimate. (iso.org)
  • One hypothesis was that the chromosomes were inactive until one was activated. (wikipedia.org)
  • The other, favored hypothesis that was eventually validated was that both maternal and paternal X chromosomes are active until some mechanism inactivates one chromosome. (wikipedia.org)
  • Early in the study of XCI in early embryonic development, the original state of the two X chromosomes and the mechanism by which they differentiated into the Xa and Xi was unknown. (wikipedia.org)
  • It is known that in the inner cell mass (the embryo proper) of mice, XCI occurs randomly, while in the extra-embryonic tissues, imprinted XCI deterministically inactivates the paternal X. In early mouse embryos, the paternal X chromosome is already partially silenced at the zygote stage by imprinted XCI, suggesting that sex-chromosome dosage compensation exists from conception. (wikipedia.org)