Showing papers on "X chromosome published in 1973"
TL;DR: The frequencies and patterns of disJunction from a trivalent in nod females suggest that the distributive pairing process involves three separate events-pairing, orientation, and disjunction.
Abstract: The female meiotic mutant no distributive disjunction (symbol: nod ) reduces the probability that a nonexchange chromosome will disjoin from either a nonexchange homolog or a nonhomolog; the mutant does not affect exchange or the disjunction of bivalents that have undergone exchange. Disjunction of nonexchange homologs was examined for all chromosome pairs; nonhomologous disjunction of the X chromosomes from the Y chromosome in XXY females, of compound chromosomes in females bearing attached-third chromosomes with and without a Y chromosome, and of the second chromosomes from the third chromosomes were also examined. The results suggest that the defect in nod is in the distributive pairing process. The frequencies and patterns of disjunction from a trivalent in nod females suggest that the distributive pairing process involves three separate events-pairing, orientation, and disjunction. The mutant nod appears to affect disjunction only.
122 citations
TL;DR: Evidence that heterochromatic X and Y chromosomes can slow down the mitotic cycle of cells in culture is presented and it is proposed that some of the effects extraX and Y chromosome have on the phenotype may be related to a reduced rate of cell division during development.
Abstract: The effects of supernumerary X and Y chromosomes on various traits that can be quantitatively measured are summarised: these traits include dermatoglyphics, intelligence, birthweight, height and immunoglobulin levels. Evidence that heterochromatic X and Y chromosomes can slow down the mitotic cycle of cells in culture is presented. It is proposed that some of the effects extra X and Y chromosome have on the phenotype may be related to a reduced rate of cell division during development.
101 citations
TL;DR: A mechanism is proposed to explain the cytogenetic data on inactivation and the derivation of the eutherian system from the marsupials and the response of the sensitive site to its passage through the male may be designated as imprinting.
Abstract: In female mammals, one of the two X chromosomes present is inactivated during early development. In marsupials, the paternal X is inactivated; in eutherians, one of the two X chromosomes is inactivated at random. A mechanism is proposed to explain the cytogenetic data on inactivation and the derivation of the eutherian system from the marsupial system. In the marsupial system, a site on the X chromosome is sensitive to paternal origin: when the X chromosome is of maternal origin, this sensitive site is responsible for influencing an adjacent site, the receptor, to maintain the X in an active state; the paternal X becomes inactive. Transposition of the sensitive site to an autosome in eutherians would have two consequences. Since the receptor site of the X chromosome is no longer adjacent, the autosomal sensitive site of maternal origin would activate an X at random. The number of active X chromosomes would conform to the number of maternal sensitive sites and thus, generally, to the number of maternal sets of autosomes. The response of the sensitive site to its passage through the male may be designated as imprinting, a term used by Crouse to indicate that the behavior of Sciara chromosomes is determined by parental origin.
79 citations
TL;DR: One group of the second chromosome lines isolated from a southern Texas population of Drosophila melanogaster, which has been known to show relatively high frequencies of male recombinations, was found to increase the frequency of sex-linked recessive lethal mutations, and mapping of a portion of the sex-links indicated a distribution along the entire X chromosome, although there was a tendency of clustering towards the tip of the X chromosome.
Abstract: One group of the second chromosome lines isolated from a southern Texas population of Drosophila melanogaster, which has been known to show relatively high frequencies of male recombinations, was found to increase the frequency of sex-linked recessive lethal mutations from a control frequency of 0.18% to 1.63%. The second group, which showed a very much reduced frequency of male recombinations, was found to cause a slight increase to 0.48%, although it was not statistically significant. The first group was also tested for the recessive lethal mutation frequency in the second chromosome; the frequency increased from a control frequency of 0.28% to 2.82%. Mapping of a portion of the sex-linked lethals indicated a distribution along the entire X chromosome, although there was a tendency of clustering towards the tip of the X chromosome. One sex-linked lethal line so far tested was found to be associated with an inversion (approximate breakpoints, 14A–18A). It was suggested that the element causing male recombination might be similar to the hi mutator gene studied earlier by Ives (1950).
60 citations
TL;DR: Negative correlation between the human X chromosome and inducibility of the enzyme was clearly established and the human repressor for inducible tyrosine aminotransferase can be assigned to the X chromosome.
Abstract: The inducibility of tyrosine aminotransferase (EC 2.6.1.5) by corticosteroid hormones in rat-human hybrid clones was studied. The presence of human X chromosome activity in the cells was always associated with the suppression of tyrosine aminotransferase inducibility in all the clones examined. Negative correlation between the human X chromosome and inducibility of the enzyme was clearly established. Corticosteroid receptor was present to the same extent in hybrid cell clones that either contained or lost the human X chromosome. The human repressor for inducible tyrosine aminotransferase has a linkage relationship with glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and hypoxanthine-guanine-phosphoribosyltransferase (EC 2.4.2.8) and, therefore, can be assigned to the X chromosome.
54 citations
51 citations
46 citations
TL;DR: The chromosome banding pattern has been analyzed in clones of male and female golden hamster cells independently transformed by polyoma virus and tumors derived from these cells, and indicates that genes of expression of malignancy in these cells were located on chromosome 56 and that genes for suppression ofmalignancywere located on a piece of chromosome 53 and on chromosome 72.
Abstract: The chromosome banding pattern has been analyzed in clones of male and female golden hamster cells independently transformed by polyoma virus and tumors derived from these cells. All the tumors showed either a loss of a piece of chromosome 53 or a gain of a piece or a whole chromosome of 56. An additional 72 chromosome in one line of transformed cells was lost in the tumors derived from this line. The results support our gene balance model of malignancy and indicate that genes of expression of malignancy in these cells were located on chromosome 56 and that genes for suppression of malignancy were located on a piece of chromosome 53 and on chromosome 72. All transformed lines and their tumors showed a loss of a piece of one or both × chromosomes in male and female cells, respectively. This loss of a piece of X chromosome was also found in non-malignant revertants from polyoma-transformed cells, so that this change in the X chromosome was not specific for malignant cells.
43 citations
TL;DR: Fluorescence and Giemsa banding showed loss of chromosomal material from the distal part of chromosome No. 6 in a severely mentally and physically retarded patient with a peculiar appearance.
Abstract: A translocation of the long arm of chromosome No. 15 onto the long arm of chromosome No. 6 was observed in a severely mentally and physically retarded patient with a peculiar appearance. Fluorescence and Giemsa banding showed loss of chromosomal material from the distal part of chromosome No.6; 45,XY,tan(6;15) (6pter→6q25::15q12→15pter). The proband's father and brothers showed hyperdiploid cells and cells with rearrangements. Regular Down's syndrome was observed in a first cousin once removed.
40 citations
TL;DR: It is proposed that dosage-compensated sex-linked genes are controlled by a positively acting regulatory factor(s) of autosomal origin, and it is possible to explain dosage compensation as a consequence of general regulatory mechanisms without invoking a special device which applies only to the X chromosomes.
Abstract: The level of activity of the enzyme glucose-6-phosphate dehydrogenase was determinel in flies having seven different chromosomic constitutions. All those having an integral number of chromosomes [XAA, XXAA, XAAA, XXAAA, and XXXAAA (X=X chromosome, A=set of autosomes)] were found to have similar units of enzyme activity/mg live weight, while diploid females with a duplication and triploid females with a deficiency showed dosage effect. The amount of enzyme activity per cell, on the other hand, is also independent of the number of X's present but appears roughly proportional to the number of sets of autosomes.—It is proposed that dosage-compensated sex-linked genes are controlled by a positively acting regulatory factor(s) of autosomal origin. With this hypothesis it is possible to explain dosage compensation as a consequence of general regulatory mechanisms without invoking a special device which applies only to the X chromosomes.
40 citations
TL;DR: Two patients with the clinical picture of Turner's syndrome showed a 46,XXp— and a 46-XXq— karyotype identified by a combination of fluorescence and autoradiography that indicated that the abnormal X chromosome was of paternal origin.
Abstract: Two patients with the clinical picture of Turner's syndrome showed a 46,XXp— and a 46,XXq— karyotype identified by a combination of fluorescence and autoradiography. Autoradiography showed that the abnormal X chromosome was indicated in most cells. The Xg findings in case 1 indicated that the abnormal X chromosome was of paternal origin.
TL;DR: The observed reexpression of rat HPRT in hybrid cells derived from H PRT(-) rat cells suggests that a genetic factor from the human cell determined the expression of the rat structural gene for HPRt.
Abstract: Fusion of hypoxanthine phosphoribosyltransferase (HPRT)- rat hepatoma cells with HPRT+ human fibroblasts yielded hybrid clones that grew in HAT selective medium and contained all the rat chromosomes and one to nine human chromosomes. Among the retained chromosomes was the human X chromosome. In all clones backselected in medium containing 8-azaguanine, human X chromosome was absent. Electrophoretic analysis revealed that, without exception, hybrid clones growing in HAT medium had an active HPRT enzyme, either human or rat, or both. When these clones were backselected in 8-azaguanine, they did not show HPRT enzyme activity. Hybrids that contained the human X chromosome also had human glucose-6-phosphate dehydrogenase. The observed reexpression of rat HPRT in hybrid cells derived from HPRT- rat cells suggests that a genetic factor from the human cell determined the expression of the rat structural gene for HPRT.
TL;DR: The data indicate that all three X-linked loci segregate with the t(Xq14q) rearrangement product thus permitting their assignment to the X chromosome's long arm, and provides strong support for the assignment of NP to 14.
Abstract: The intrachromosomal localization of three X-linked gene loci (PGK, HGPRT and G6PD) has been determined using a somatic cell genetic approach. A human cell line possessing an X/14 translocation was used as one parent in the formation of human/mouse hybrids. The translocation separates the human X into two parts: Xp and t(Xq14q). The data indicate that all three X-linked loci segregate with the t(Xq14q) rearrangement product thus permitting their assignment to the X chromosome's long arm. Secondary rearrangements and data from other laboratories suggest that the order of the the three markers from the centromere to the distal end of the X long arm is PGK, HGPRT, G6PD. It was also observed that NP, an autosomal locus, segregated with the t(Xq14q) chromosome. This provides strong support for the assignment of NP to 14.
TL;DR: The bobbed (bb) locus in Drosophila melanogaster is characterized by short, thin bristles, prolonged developmental time and thinning of the cuticle, commonly referred to as etching.
Abstract: Mutants at the bobbed (bb) locus in Drosophila melanogaster are characterized by short, thin bristles, prolonged developmental time and thinning of the cuticle, commonly referred to as etching1. Extensive variability of expression of bb mutants is a classical observation-some alleles are visually undetectable from wild-type ones whereas other alleles are lethal. Classical genetic analyses have placed the locus of bb alleles in the proximal heterochromatic region of the X chromosome close to the nucleolar organizer (NO) region and in the short arm of the Y chromosome, again near the NO2. A high frequency of reversion is characteristic of bb mutants1.
TL;DR: A translocation of the Y to the X chromosome was found in a woman who had habitual abortion and she has a rare form of dwarfism and abnormal dermatoglyphic patterns.
Abstract: A translocation of the Y to the X chromosome was found in a woman who had habitual abortion. Endocrinologic studies disclosed only an abnormal elevation of her prolactin and thyroid-stimulating hormone (TSH) levels. Phenotypically, she has a rare form of dwarfism and abnormal dermatoglyphic patterns. This new chromosomal rearrangement in the human has several implications.
TL;DR: The data from this study, along with that on gene linkage of human hemophilia A and B, provide support for the thesis of homology of the X chromosome during speciation.
TL;DR: The Lyon principle of X chromosome inactivation, somatic cells of mammalian females form random mosaic populations resulting from irreversible and heritable differentiation of the two X chromosomes at an early stage of development, is supported.
Abstract: ACCORDING to the Lyon principle of X chromosome inactivation, somatic cells of mammalian females form random mosaic populations resulting from irreversible and heritable differentiation of the two X chromosomes at an early stage of development. One X chromosome remains capable of gene transcription, the other becomes unresponsive to inducers and remains genetically inert1. Consequently, any one cell only expresses genes that are located on either the maternal or paternal X chromosome. Data in support of this principle have come from in vivo studies of X-linked murine coat colour genes2 and in vitro studies of X-linked human genes that are expressed in cultured cells3. Furthermore, two non-allelic X-linked loci tested in the same population of cloned cells are expressed in the cis position as would be expected from a single parental contribution8.
TL;DR: The sex-linked Pgd+ and Zw+ genes of Drosophila melanogaster and their associated enzyme activities 6-phosphogluconate dehydrogenase and glucose 6- phosphate dehydration were employed in an analysis of the relationship between dosage compensation and the location of genes in the genome.
Abstract: The sex-linked Pgd+ and Zw+ genes of Drosophila melanogaster and their associated enzyme activities 6-phosphogluconate dehydrogenase and glucose 6-phosphate dehydrogenase were employed in an analysis of the relationship between dosage compensation and the location of genes in the genome. In the genotypes examined, the enzyme activity specified by each copy of the gene is twice in males what it is in females. This is true of normal, structurally rearranged, and duplication genotypes. Dosage compensation, therefore, is a regulatory function associated with single structural genes or small chromosomal segments and does not depend on the gene's physical location on the X chromosome.
TL;DR: The preponderance of homozygotes for each type of X chromosome in populations, suggested the probable role of sex chromosomes heterochromatin in speciation.
Abstract: Bandicota bengalensis bengalensis (Gray) trapped from different localities of India and Nepal exhibited a marked variation in the size and morphology of sex chromosomes. Three types of X's were found; A) simple acrocentric, B) composite subtelocentric and C) composite submetacentric X with their relative sizes 5.9%, 7.5% and 9.6% of the genome respectively. The autosomes remained unaltered. It was shown that this variation in the size of sex chromosomes was caused by deletion of constitutive heterochromatin. The Y chromosome was also found to be variable. Usually a large X was combined with a large Y. The preponderance of homozygotes for each type of X chromosome in populations, suggested the probable role of sex chromosomes heterochromatin in speciation.
TL;DR: A 20-year-old aphasic, severely retarded girl with multiple abnormalities but normal menstruation was studied by fluorescence microscopy, autoradiography, and the G-band-ing method.
Abstract: A 20-year-old aphasic, severely retarded girl with multiple abnormalities but normal menstruation was studied by fluorescence microscopy, autoradiography, and the G-band-ing method. Autosome material
TL;DR: An abnormally large X chromosome was found in a girl with Turner's syndrome, and was identified as a X/X translocation (karyotype 45,X/46,X,-X,+t(XqXp)).
Abstract: An abnormally large X chromosome was found in a girl with Turner's syndrome, and was identified as a X/X translocation (karyotype 45,X/46,X,-X,+t(XqXp)).
TL;DR: Most of the previously published associations have been based on composite data representing collections made in several seasons and several years, and the present paper reexamines this material and presents data from several additional localities in which collections were made at three or more times of the year.
Abstract: The classic models of Fisher, Haldane, Wright and others which established the modern (neo-Darwinian) understanding of evolution emphasize the distribution of alleles at a single locus. Evolutionists have long realized, however, that most significant adaptations have probably involved the interaction of many loci. In fact, part of the initial interest in the inversion polymorphisms in Drosophila pseudoobscura and Drosophila junebris stemmed from the recognition that these chromosomal changes represent selection for multiple interacting genes which can be interpreted within the framework of single locus theory, inasmuch as most inversions of these species act generally as allelic blocs, or \"supergenes.\" Beginning in 1954 the author (Levitan, 1954, 1955, 1958, 1961a, 1961b, 1964) discovered evidence that selection may OCCur for linked interacting loci which are not part of allelic blocs, which is to say that mechanisms exist to counter the normal tendency of recombination to force such widely separated genes into random equilibriums. In Drosophila robusta Sturtevant, both of the largest chromosomes, the X-chromosome and chromosome 2, are metacentrics, and all four arms exhibit widespread inversion polymorphisms. The writer found that in a number of localities the linked arrangements of these chromosomes persist in non-random associations (linkage disequilibriums), and that the phenomenon occurs in many species (see reviews by Levitan, 1958, and Martin, 1965). Carson (1958) presents a more general review of D. robusta and its cytogenetics. Most of the previously published associations have been based on composite data representing collections made in several seasons and several years. The present paper reexamines this material and presents data from several additional localities in which collections were made at three or more times of the year. The results often show recurrent variations in the frequencies of certain gene arrangements. Many of these cyclic changes occur, however, in only one of the several linkage combinations possible for the arrangements. In fact some temporal differences that appear among linkage combinations are not apparent in the analysis of the component arrangements. Partial reports of the results have appeared in abstracts (Levitan, 1957, 1971).
TL;DR: Results show that an additional class of mutations resulting from chromosome breakage accounts for the increased mutational frequency when the yellow locus is adjacent to heterochromatin.
Abstract: Ethyl methanesulfonate (EMS)-induced mutations involving the yellow locus of Drosophila melanogaster were studied, both when the dominant alleles for yellow ( y + ) and closely linked achaete ( ac + ) were adjacent to euchromatin in their normal position on the left end of the X chromosome and when adjacent to constitutive heterochromatin on the Y chromosome. A yellow mutation was considered intragenic if the adjacent achaete locus was not affected. The intragenic mutation frequency did not change with the position of the yellow locus in the genome; however, the total mutation frequency was three-fold higher when the yellow locus was positioned adjacent to consititutive heterochromatin. Results show that an additional class of mutations resulting from chromosome breakage accounts for the increased mutational frequency when the yellow locus is adjacent to heterochromatin.
TL;DR: The patterns of breaks and exchanges induced by X irradiation of human lymphocytes obtained from individuals with abnormal sex-chromosome complements have been analyzed and compared with similarly individuated individuals.
Abstract: The patterns of breaks and exchanges induced by X irradiation of human lymphocytes obtained from individuals with abnormal sex-chromosome complements have been analyzed and compared with similarly ind
TL;DR: Sex chromatin studies revealed variable numbers of X-chromatin bodies of smaller than normal size and trypsin-Giemsa banding of the chromosomes demonstrated the deletion of part of the long arm of an X chromosome.
Abstract: An 18-year-old girl had short stature, secondary amenorrhea, and an elevated level of serum gonadotrophins. Sex chromatin studies revealed variable numbers of X-chromatin bodies of smaller than normal size. Trypsin-Giemsa banding of the chromosomes demonstrated the deletion of part of the long arm of an X chromosome.
TL;DR: It is concluded that rDNAs of normal X and Y chromosomes have opposite orientation with respect to the centromere and the implications of this observation are discussed.
Abstract: We tested for recombination within the DNA that codes for ribosomal RNA (rDNA) on the X and Y chromosomes of Drosophila melanogaster. The criterion was the appearance of intermediate bb alleles on X-Y recombinants from wild bb+ and lethal bb1 loci carried on parental chromosomes. Recombination within the rDNA occurs only when the rDNA of the X chromosome is inverted. We conclude that rDNAs of normal X and Y chromosomes have opposite orientation with respect to the centromere. The implications of this observation are discussed.
TL;DR: A phenotypically normal woman has an apparently balanced reciprocal translocation between chromosomes No. 9 and No. 18 (translocation 9p-; 18p+), which was transmitted in an unbalanced state to an infant and a fetus.
Abstract: A phenotypically normal woman has an apparently balanced reciprocal translocation between chromosomes No. 9 and No. 18 (translocation 9p-; 18p+), which was transmitted in an unbalanced state to an infant and a fetus. In the latter instance, chromosome analysis of cultured amniotic cells disclosed an abnormal karyotype, which was identical to that of the first affected child. The therapeutically aborted fetus was grossly abnormal and resembled the affected child. The physical features noted are those frequently associated with chromosome abnormalities, although not diagnostic for any specific syndrome. We presume that the chromosome abnormality in the affected offspring represents partial duplication of the short arm of chromosome No. 9 and partial deletion of the short arm of chromosome No. 18. No marked resemblance is noted between these cases and reported cases of trisomy 9 or of partial deletion of the short arm of 18.
Journal Article•
TL;DR: It is suggested that XX (ring)XO mosaicism permitted expression of the abnormal X-linked gene.
Abstract: Severe factor IX deficiency (Christmas disease) in a phenotypically normal girl prompted a cytogenetic study of the proband and her parents which showed, in the patient, a karyotype with 46 chromosomes (XX ring) and a karyotype comprised of 45 chromosomes with a single X chromosome (45XO). The parents were cytogenetically normal. The activity of factor IX in the patient was markedly abnormal (less than 1%). It is suggested that XX (ring)XO mosaicism permitted expression of the abnormal X-linked gene.