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Showing papers on "X chromosome published in 1978"


Journal ArticleDOI
TL;DR: It is shown that this creates a selection pressure for differentially increasing the activity of the X chromosome in heterogametic individuals at the expense of that of the Y, leading eventually to a genetically inert Y chromosome and to the evolution of dosage compensation.
Abstract: Some difficulties with the classical model for the evolution of a genetically invert Y chromosome are discussed. An alternative model is proposed, which is based on the principle of Mullers ratchet; this involves the accumulation of chromosomes bearing deleterious mutant genes in a finite population in the absence of crossing-over. This process would result in the gradual increase, with time, in the number of mutant loci carried in an average Y chromosome, although the frequency of individual deleterious alleles at most loci remains low. It is shown that this creates a selection pressure for differentially increasing the activity of the X chromosome in heterogametic individuals at the expense of that of the Y, leading eventually to a genetically inert Y chromosome and to the evolution of dosage compensation.

396 citations


Journal ArticleDOI
03 Aug 1978-Nature
TL;DR: The method which facilitates determination of the sex of the embryonic material being assayed has led to the demonstration that early male and female mouse blastocysts differ twofold in HGPRT activity, a finding indicative of uncompensated X- chromosome dosage dependent gene activity before X-chromosome inactivation.
Abstract: ALTHOUGH neither X chromosome of preimplantation female mammalian embryos exhibits the two cytological signs of inactivation and dosage compensation—heteropyknosis and late replication1,2—it has not been known whether both X chromosomes actually function during this period. Biochemical evidence based on increasing hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity during the mouse morula stage indicates that at least one X chromosome is functional3,4. This is corroborated by the observation that mouse embryos lacking an X chromosome do not survive beyond the early cleavage stages5. The principal approach to determining whether both X chromosomes are functional before inactivation has been to look at the distributions of the activities of known X-linked enzymes in individual embryos6,7. A bimodal distribution would be expected if dosage compensation had not yet occurred and female embryos with two X chromosomes made twice as much enzyme as male embryos with only one. However, identities of the embryos being assayed are not known, and conclusions based on activity distributions are necessarily inferential. We have circumvented this difficulty by using a method which facilitates determination of the sex of the embryonic material being assayed. This has led to the demonstration that early male and female mouse blastocysts differ twofold in HGPRT activity, a finding indicative of uncompensated X-chromosome dosage dependent gene activity before X-chromosome inactivation.

209 citations


Journal ArticleDOI
17 Nov 1978-Science
TL;DR: It is proposed that in both groups of organisms the evolution of heteromorphic sex chromosomes was gradual and occurred as the direct result of the Evolution of dosage compensation rather than the reverse.
Abstract: Dosage compensation is a mechanism by means of which the activity of X-linked or Z-linked genes is made equal in the two sexes of organisms with an XX compared to XY or ZZ compared to ZW basis of sex determination. In mammals, compensation is achieved by the inactivation of one X chromosome in somatic cells of females. In Drosophila, compensation does not involve inactivation. The two X chromosomes in females as well as the single X in males are regulated, and individual genes are thought to respond independently to the regulatory mechanism. It is proposed that in both groups of organisms the evolution of heteromorphic sex chromosomes was gradual and occurred as the direct result of the evolution of dosage compensation rather than the reverse.

159 citations


Journal ArticleDOI
07 Dec 1978-Nature
TL;DR: Evidence is presented that gross structural changes involving the X chromosome are the genetic basis of a significant proportion of radiation-induced mutation to TG resistance in cultured human fibroblasts.
Abstract: RESISTANCE to the cytotoxic purine analogue 6-thioguanine (TG) in cultured mammalian cells is known to be associated with deficiency in the X-chromosome-linked purine-salvage enzyme, hypoxanthine-guanine phosphoribosyl transferase (HGPRT, EC 2.4.2.8). The induction of mutations to TG resistance in cultured mammalian cells has been used to quantify the mutagenic effects of various physical and chemical agents1–3 and it has been argued that such mutations arise primarily as a result of true gene mutations4. However, because ionising radiation induces TG-resistant mutants with very low HGPRT activity5 and fails to induce the ouabain-resistance phenotype in mammalian cells6,7, it has been suggested that ionising radiation leads to gross genetic damage rather than to point mutations in structural genes2,7. Here we present evidence that gross structural changes involving the X chromosome are the genetic basis of a significant proportion of radiation-induced mutation to TG resistance in cultured human fibroblasts.

125 citations


Journal ArticleDOI
26 Jan 1978-Nature
TL;DR: Evidence is presented that both X chromosomes are genetically active in clonal cultures of undifferentiated female mouse teratocarcinoma stem cells derived from a spontaneous ovarian tumour.
Abstract: Evidence is presented that both X chromosomes are genetically active in clonal cultures of undifferentiated female mouse teratocarcinoma stem cells derived from a spontaneous ovarian tumour. As the cells differentiate in vitro one of the X chromosomes becomes inactivated.

124 citations


Journal ArticleDOI
03 Aug 1978-Nature
TL;DR: Evidence is presented for the activity of both the maternal and paternal X chromosomes by the eight-cell stage, with inactivation initiated at blastulation.
Abstract: TO compensate for unequal doses of genes on the X chromosomes of males and females, one of the X chromosomes in the somatic cells of mammalian females is inactive1. This inactivation occurs early in development, although the exact time is unknown2. Before X-chromosome inactivation, and in the absence of other dosage compensating mechanisms, female embryos with two X chromosomes would be expected to have twice as much activity for an X-linked enzyme as male embryos with only one X chromosome. In a litter with approximately an equal number of male and female embryos, the distribution of enzyme activity should have two equal-sized peaks separated by a factor of two. The change from a bimodal to unimodal distribution would indicate that X-chromosome inactivation had occurred. Early in development, the X-linked enzymes α-galactosidase (α-gal)3 and hypoxanthine guanine phosphoribosyltransferase (HGPRT)4,5 are both derived from embryonic gene activity. α-gal was found to have a bimodal distribution at the morula stage3. For HGPRT, Monk and Kathuria6 found no bimodality at either the eight-cell or blastocyst stages, however further analysis revealed bimodality at certain stages7. Epstein et al.8 have found that females have twice as much HGPRT activity as males in early blastocysts. We present here evidence for the activity of both the maternal and paternal X chromosomes by the eight-cell stage, with inactivation initiated at blastulation.

119 citations


Journal ArticleDOI
13 Jul 1978-Nature
TL;DR: The mouse gene map based on sexual genetics has been expanded by analysis of interspecific somatic cell hybrids segregating mouse chromosomes, so that the genetic maps of man and mouse can be compared.
Abstract: WHILE genes on the X chromosome have been conserved during evolution1 little is known about the degree of conservation of autosomal synteny groups for species distantly related in evolution such as mouse and man. The mouse gene map based on sexual genetics2,3 has been expanded by analysis of interspecific somatic cell hybrids segregating mouse chromosomes, so that the genetic maps of man and mouse can be compared. The available information indicates that genes located on different arms of the same human chromosome are not syntenic in the mouse, and genes which are many map units apart (25–45 cM) in the mouse are unlikely to be syntenic in man4–6. In contrast, genes that are tightly linked (less than 1 cM apart) seem to remain syntenic during evolution5. In addition, in species closely related in evolution, such as mouse and rat,7 or man and non-human primates8, several homologous genes have been assigned to chromosomes that are apparently homologous by chromosome banding. Five genes in the mouse (Eno-1, Pgd, Pgm-2, Ak-2, Gpd-1) are syntenic9–11 and their human homologues have been assigned to human chromosome 1; all but the human homologue of Gpd-1 are regionally assigned to arm 1p (refs 4 and 12). This apparent conservation of a rather large autosomal synteny group prompted us to investigate the extent of conservation of other autosomal regions. The results have provided chromosomal assignments for seven gene loci in the mouse and evidence for synteny of four pairs of gene loci on four different human and mouse autosomes.

99 citations


Journal ArticleDOI
06 Oct 1978-Science
TL;DR: Evidence is presented for the existence of a gene, probably on the X chromosome, which prevents testis differentiation when present in 46,XY human embryos, and affected 46, XY women are not completely normal because of premature ovarian involution.
Abstract: Evidence is presented for the existence of a gene, probably on the X chromosome, which prevents testis differentiation when present in 46,XY human embryos. Affected 46,XY women are not completely normal because of premature ovarian involution, as a result of which they have "streak gonads" similiar to those of 45,X women.

94 citations


Journal ArticleDOI
TL;DR: A total of 941 mouse blastocysts obtained from two types of crosses in which one of parents carried Cattanach's X/autosome translocation was studied cytogenetically by quinacrine mustard fluorescence, finding a preferential choice of Xp at the blastocyst stage might have an important bearing upon the preponderance of cells with an inactive Xp in the chorion and yolk-sac splanchnopleure.
Abstract: A total of 941 mouse blastocysts obtained from two types of crosses in which one of parents carried Cattanach’s X/autosome translocation was studied cytogenetically by quinacrine mustard fluorescence. The rearranged X (Xt) and the normal X (Xn) were distinguished by size. Karyotype analysis was successful in 721 embryos, of which 205 were heterozygous for Cattanach’s translocation. A single heterochromatic and brightly fluorescent X chromosome was identified in 154 metaphase spreads from 89 blastocysts consisting of 32–96 cells. The paternally derived X chromosome (Xp) was heterochromatic in 87 % and 88 % of the informative cells from the crosses XtXn × XtY and XtXn × χnγ; respectively. This preferential choice of Xp at the blastocyst stage might have an important bearing upon the preponderance of cells with an inactive Xp in the chorion and yolk-sac splanchnopleure.

74 citations


Journal ArticleDOI
TL;DR: At least three X-linked genes have been transferred from one cell to another with high frequency, using metaphase chromosomes.
Abstract: Transfer of genes from one type of cultured mammalian cell to another by using isolated metaphase chromosomes has been reported with a frequency of one per 106-108 cells. Very recently a rate of 16/106 has been reported with Chinese hamster ovary cells [Spandidos, D. A. & Siminovitch, L. (1977) Proc. Natl. Acad. Sci. USA 74, 3480-3484]. To increase the frequency of gene transfer, we isolated metaphase chromosomes from hypoxanthine guanine phosphoribosyltransferase (HGPRT) positive cells, entrapped them in liposomes, and fused the lipochromosomes with HGPRT-negative cells. Lipochromosomes were prepared with cholesterol and egg lecithin, using isolated metaphase chromosomes from a mouse-human somatic hybrid cell line (A9/HRBC2); the entire X chromosome, including the HGPRT, glucose-6-phosphate dehydrogenase, and phosphoglycerate kinase genes, is the only recognizable human genetic material retained by the hybrids. Enclosure of the chromosomes in the lipid envelope was confirmed by electron and fluorescence microscopy and differential centrifugation. These lipochromosomes were fused with HGPRT- mouse cells (A9) in the presence or absence of polyethylene glycol and transferents were selected in hypoxanthine/aminopterin/thymidine (HAT) medium. The frequency of transfer was at least once per 105 cells, a minimum 10-fold improvement over previous methods. The selected cells contained HGPRT activity similar to the amount found in the A9/HRBC2 cells. Starch gel electrophoresis verified that the observed HGPRT activity in the transferents is due to the human enzyme. Human glucose-6-phosphate dehydrogenase and phosphoglycerate kinase were also identified electrophoretically in the transferents. Karyotyping with C and Q banding did not reveal the presence of the whole human X chromosome or a visible extra fragment of a human chromosome associated with the mouse genome. The biochemical data strongly suggest, however, that transfer of a portion of the human X chromosome has occurred in these transferents. Thus, at least three X-linked genes have been transferred from one cell to another with high frequency, using metaphase chromosomes.

71 citations


Journal ArticleDOI
TL;DR: It appears that in males of this species the Y chromosome and an autosome have fused to form a metacentric chromosome.
Abstract: Chromosomes of 21 sockeye salmon [Oncorhynchus nerka (Walbaum)] from three locations in Washington state were examined. All males had 57 chromosomes, while all females had 58 chromosomes. Both sexes had 104 chromosome arms. It appears that in males of this species the Y chromosome and an autosome have fused to form a metacentric chromosome.

Journal ArticleDOI
TL;DR: Preerential expression of the maternal X chromosome, as has been shown in marsupials and in extraembryonic membranes of rodents and now in man, may reflect the state of activity of the X chromosomes in the early stages of female embryonic development.
Abstract: In placenta membranes of newborn girls carrying electrophoretically distinguishable G6PD alleles, the maternally derived isozyme is expressed preferentially. This phenomenon cannot be explained by allelic differences in enzyme activity or by somatic selection directed against cells with particular G6PD phenotypes. Instead, it may be that in this tissue X inactivation is nonrandom. Preferential expression of the maternal X chromosome, as has been shown in marsupials and in extraembryonic membranes of rodents and now in man, may reflect the state of activity of the X chromosomes in the early stages of female embryonic development.

Journal ArticleDOI
01 Mar 1978-Cell
TL;DR: It is concluded that this sequence is related to human satellite III, but shows considerable differences in structure.

Journal ArticleDOI
TL;DR: It is shown in the present paper that the two types of X chromosomes, X and X*, exhibit differences in the G-band patterns of their short arms.
Abstract: In the wood lemming (Myopus schisticolor) three genetic types of sex chromosome constitution in females are postulated: XX, X*X and X*Y (X*=X with a mutation inactivating the male determining effect of the Y chromosome). Males are all XY. It is shown in the present paper that the two types of X chromosomes, X and X*, exhibit differences in the G-band patterns of their short arms. In addition, it was demonstrated in unbanded chromosomes that the short arm in X* is shorter than in X. The origin of these differences is still obscure; but they allow to identify and to distinguish the individual types of sex chromosome constitution, as of XX versus X*X females and of X*Y females versus XY males, on the basis of G-banded chromosome preparations from somatic cells.

Journal ArticleDOI
TL;DR: Two maternal male cousins in a Jewish Iraqi kindred were affected with dyskeratosis congenita and had a megaloblastic bone marrow and Chromosomal studies showed a 46XY karyotype in both cases; however, nonspecific numerical aberrations and structural abnormalities were found.
Abstract: • Two maternal male cousins in a Jewish Iraqi kindred were affected with dyskeratosis congenita and had a megaloblastic bone marrow. One cousin had pancytopenia and the other had thrombocytopenia. The kindred displays a deficiency of glucose-6-phosphate dehydrogenase (G6PD) and a β-thalassemia trait. The following genetic "markers" of the X chromosome were studied: G6PD, the X-linked blood groups Xg, and color vision. Linkage analysis indicated that dyskeratosis, G6PD, and Xg are far apart on the X chromosome. Chromosomal studies showed a 46XY karyotype in both cases; however, nonspecific numerical aberrations and structural abnormalities were found in the first and in the second case, polyploidy was seen in four of 60 cells. The proband's cultured fibroblasts did not show increased susceptibility to malignant transformation by simian virus 40, an oncogenic virus. (Arch Dermatol114:1667-1671, 1978)

Book ChapterDOI
Nobuo Takagi1
TL;DR: Nonrandomness was assessed from studies made on differentiated cells remote from early embryonic cells in which inactivation occurred, and it is not clear whether nonrandom inactivation, or a secondary event(s) after random inactivation).
Abstract: Random X-chromosome inactivation makes the female of placental mammals a natural mosaic for clones of cells having either the maternally derived X (Xm) or paternally derived one (XP) genetically inactivated (Lyon 1961). In marsupials, on the other hand, preferential inactivation of the paternally inherited X chromosome seems to be a rule in most tissues (Sharman 1971; Cooper, Johnston, Murtagh, Sharman, VandeBerg, and Poole 1975). There are, however, instances in which inactivation is obviously not random in placental mammals (Lyon 1974). Nonrandomness was assessed from studies made on differentiated cells remote from early embryonic cells in which inactivation occurred. Thus it is not clear whether nonrandom inactivation, or a secondary event(s) after random inactivation, was responsible for the ultimate nonrandom expression.

Journal ArticleDOI
24 Aug 1978-Nature
TL;DR: This work has been able to resolve the two classes of spermatids by pulse cytophotometry (that is, flow microfluorometry) - X and Y sperm, which carry the autosomes plus the Y chromosome.
Abstract: SEPARATION of sperm bearing X and Y chromosomes is limited by, among other difficulties, the inability to distinguish between the two cell types. The two types of sperm can be distinguished only in man because the Y chromosome is highly fluorescent when stained with quinicrine mustard1. Because of the greater length of the X chromosome than the Y chromosome, it is expected that X-bearing sperm will have a greater DNA content. Based on chromosome length measurements2, the difference in DNA content between X-bearing sperm of the mouse (Mus musculus), which carry 19 autosomes plus the X chromosome, and the Y-bearing sperm, which carry the autosomes plus the Y chromosome, is expected to be 3.4%. Distinguishing X and Y sperm on the basis of this difference requires a method of measurement of DNA content with high precision. We have been able to resolve the two classes of spermatids by pulse cytophotometry (that is, flow microfluorometry).

Journal ArticleDOI
TL;DR: The meiotic behaviour of a balanced translocation involving the short arms of chromosomes 5 and 22 has been analyzed by reconstructions of lateral components and synaptonemal complexes at early and mid pachytene in human spermatocytes to conclude that the translocation is reciprocal with transfer of the telomere region from chromosome 22 to chromosome 5 and that of the latter to chromosome 22.
Abstract: The meiotic behaviour of a balanced translocation involving the short arms of chromosomes 5 and 22 has been analyzed by reconstructions of lateral components and synaptonemal complexes at early and mid pachytene in human spermatocytes. At early pachytene, the normal chromosome 5 and the segment translocated onto chromosome 22 are paired with a synaptonemal complex in all 8 nuclei reconstructed, while pairing between the normal chromosome 22 and the translocation chromosome 5 was never observed. The pairing pattern was less regular at mid pachytene where a quadrivalent was observed in only 3 out of the 4 nuclei analyzed, while in the fourth nucleus, pairing was in part nonhomologous: the segment translocated onto chromosome 22 exhibited foldback pairing with itself and the short arm of the normal chromosome 5 was paired with the differential segment of the X chromosome. The short arms of translocation chromosome 5 and the normal chromosome 22 were paired in only one mid pachytene nucleus. Translocation chromosome 5 possessed in all 4 nuclei a 200 nm long terminal region of condensed chromatin resembling the heterochromatin of the short arms of the acrocentric chromosomes. This together with the observation that the telomere of the short arm of translocation chromosome 5 was attached to the nuclear envelope permits the conclusion that the translocation is reciprocal with transfer of the telomere region from chromosome 22 to chromosome 5 and that of the latter to chromosome 22. Recombination nodules were more frequent in bivalent 5 than in the remainder of the genome whereas a similar increase in nodule frequency was not observed for bivalent 22.

Journal ArticleDOI
TL;DR: Differences probably reflect variation at an JT-chromosome controlling element locus among inbred strains of mice, similar to that described by Cattanach & Williams (1972) using X-linked morphological markers, although this has yet to be tested.
Abstract: The proportions of the two isozyme bands of the X-linked form of phosphoglycerate kinase (PGK-1) were compared in 16 tissues from four groups of adult heterozygous females. Little evidence was found for differences in expression of the two isozymes among tissues but there was a marked difference among the four groups of mice. The proportion of the PGK-1B enzyme was consistently lower in PGK-1AB heterozygous daughters of C3H/HeHa females than in corresponding heterozygotes with a C57BL/6Ha, DBA/2Ha or JBT/Jd mother. This difference was also observed in foetuses on the fourteenth day of gestation irrespective of whether the C3H/HeHa X chromosome was derived from the mother or the father. Sequential sampling of blood from the same heterozygous females provided no evidence for genetically determined cell selection in the adult erythropoietic tissue. The observed differences probably reflect variation at an X-chromosome controlling element locus among inbred strains of mice, similar to that described by Cattanach & Williams (1972) using X-linked morphological markers, although this has yet to be tested.

Journal ArticleDOI
TL;DR: These findings provide an explanation for the phenotype: Klinefelter syndrome plus a few mild malformations that are sometimes seen in this syndrome but are also seen in duplication of the proximal portion of chromosome 14.
Abstract: In the KOP translocation, t(X;14)(q13;q32), virtually the entire long arm of the X has been translocated to the end of the long arm of chromosome 14. Meiotic secondary nondisjunction in a female balanced carrier of the translocation has led to a son with two der(14) or 14-X chromosomes. The normal X chromosome is late replicating in the mother. One of the two 14-X chromosomes is late replicating in the son, with heavy terminal labeling of all but the centromeric end of the chromosome. This suggests that genetic inactivation has spread from the Xq segment of the translocation chromosome to at least two thirds of the segment derived from chromosome 14, and that the remaining proximal segment of chromosome 14 is possibly still genetically active. These findings provide an explanation for the phenotype: Klinefelter syndrome plus a few mild malformations that are sometimes seen in this syndrome but are also seen in duplication of the proximal portion of chromosome 14. Although the proband has a duplication of virtually an entire chromosome 14, 14(pter leads to q32), the phenotypic effect of the autosomal duplication has been mostly nullified by the spread of inactivation.

Journal ArticleDOI
09 Feb 1978-Nature
TL;DR: It is reported here that diploid parthenogenetic mouse embryos, at the late egg cylinder stage, showed a single late replicating chromosome, indicating that X inactivation had occurred normally, and it seems that neither passage of chromosomes through male gametogenesis, nor fertilisation, nor probably the effects of peripheral egg cytoplasm are required for normal X in activation in the mouse.
Abstract: THE mechanism by which one X chromosome in normal cells of female mammals becomes inactive while the other, apparently identical, chromosome remains active is not known. In kangaroos the paternally derived X chromosome is preferentially inactivated in most tissues1, and in mice and rats similar preferential inactivation of the paternal X chromosome occurs in the cells of the extraembryonic membranes2,3. Paternal X inactivation in kangaroos led Cooper4 to postulate that passage of the X chromosome through male gametogenesis was an important factor in its inactivation. He4 and Brown and Chandra5 suggested that paternal X inactivation was a primitive form and that random X inactivation as seen in adult eutherian mammals had evolved from it. Brown and Chandra further suggested that passage of one chromosome set through male gametogenesis or fertilisation led to chromosomal imprinting. A locus concerned in the control of X chromosome activity was postulated to become inactive when imprinted, and one active copy of this gene could maintain the activity of one X chromosome. In marsupials this gene was postulated to lie on the X chromosome itself, but on an autosome in euitherians. Thus, in eutherians the number of active X chromosomes in any animal should be equal to the number of maternally derived (and therefore non-imprinted) autosome sets. In this context it is interesting to study X inactivation in artificially formed parthenogenetic embryos, in which all chromosomes are of maternal origin. We report here that diploid parthenogenetic mouse embryos, at the late egg cylinder stage, showed a single late replicating chromosome, indicating that X inactivation had occurred normally. Because in the production of these embryos polar body formation had been suppressed, it seems that neither passage of chromosomes through male gametogenesis, nor fertilisation, nor probably the effects of peripheral egg cytoplasm are required for normal X inactivation in the mouse.

Journal ArticleDOI
01 Feb 1978-Heredity
TL;DR: Chromosome substitution lines derived from two inbred strains of Drosophila melanogaster homozygous for the Adhs allele of alcohol dehydrogenase but differing significantly in ADH activity have been analysed.
Abstract: Chromosome substitution lines derived from two inbred strains of Drosophila melanogaster homozygous for the AdhS allele of alcohol dehydrogenase but differing significantly in ADH activity have been analysed. Variation in activity can be attributed to all three major chromosomes. The effect of the second chromosome, where the ADH structural gene is located, can be modified significantly by the genotype of both the first and the third chromosomes. The most substantial single effect results from homozygous differences between the third chromosomes. In contrast, differences between the X chromosomes are revealed only when the second or second and third chromosomes are heterozygous.

Journal ArticleDOI
TL;DR: Cytogenetic studies on a mentally retarded boy revealed an X-Y translocation, karyotype 46,X,t(X;Y)(p22;q11), suggesting non-random inactivation of the normal maternally derived X chromosome, and that the non-inactivated X- Y translocation chromosome included the locus for male determination.
Abstract: Cytogenetic studies on a mentally retarded boy revealed an X-Y translocation, karyotype 46,X,t(X;Y)(p22;q11). Only 5 other such cases have been reported and these were all females. The unequivocal male phenotype suggested non-random inactivation of the normal maternally derived X chromosome, and that the non-inactivated X-Y translocation chromosome included the locus for male determination. Confirmation of this was provided by unassociated X and Y chromatin in interphase cells, as well as by reverse banding after BrdU incorporation and autoradiography of metaphase chromosomes. There was anomalous Xg blood group inheritance in the proband, indicating possible localisation of the Xg locus to the terminal portion of the X short arm. Linkage of Xg and a form of X-linked mental retardation is suggested. Close linkage of the Xg locus with the loci for alpha-galactosidase, phosphoglycerate kinase, G-6-PD, and MPS II was excluded.

Journal ArticleDOI
TL;DR: Results of Xga typing of erythrocytes suggest that the Xg locus is on the short arm of the X chromosome, and it is believed that families of persons with structural chromosomal abnormalities should be studied to exclude familial transmission.
Abstract: Seven women in three generations of a family have been affected by Turner syndrome. Turner phenotype in this family is the result of deletion of the entire short arm of one X chromosome. The short arm deletion is transmitted by carriers of a balanced X-1 translocation. Autoradiographic findings showed that the deleted X chromosome was late labeling in those persons with Turner syndrome, whereas the normal X chromosome was late replicating in carriers of the balanced translocation. The results of Xga typing of erythrocytes suggest that the Xg locus is on the short arm of the X chromosome. Because of the clinical implications, we believe that families of persons with structural chromosomal abnormalities should be studied to exclude familial transmission.

Journal ArticleDOI
TL;DR: The findings in the patient with X/21 translocation support the hypothesis of the existence of one inactivation center on Xq, and can be explained by random inactivation and subsequent selection against specific cell lines.
Abstract: We describe an X/15 translocation which was balanced in a phenotypically normal mother [46,X,t(X;15)(p22;q15)] and unbalanced in her phenotypically abnormal daughter [46,X,der(X),t(X;15)(p22;q15)mat]. A third case involves a balanced X/21 translocation in a girl with a multiple congenital anomaly-retardation syndrome [46,X,t(X;21)(p11;p11?)]. 5-BrdU acridine orange banding on lymphocytes revealed late replication of the normal X chromosome in the mother and of the normal or abnormal X chromosome in the two other cases. Our findings are only partially consistent with previous observations. All X-inactivation patterns can be explained by random inactivation and subsequent selection against specific cell lines. Furthermore, the findings in our patient with X/21 translocation support the hypothesis of the existence of one inactivation center on Xq.

Journal ArticleDOI
01 May 1978-Genetics
TL;DR: It is proposed that the sequestering of DNA satellite I in the centromeric heterochromatin of chromosome 2 (but not in X or 3) may account for the increase in recombination, and the question of independent control of interference and recombination is discussed.
Abstract: Heat and interchromosomal effects on recombination have been compared for 23 regions comprising the predominantly euchromatic portions of the five arms of the Drosophila genome Patterns of response are strikingly similar, with both modifiers causing proximal and distal increases and minimal effects in the middle of the arms Changes in interference for the same regions in the presence of the two modifiers reveal little similarity, except for the X chromosome The question of independent control of interference and recombination, as well as alternatives for their temporal sequence, is discussed Recombination response to the two modifiers in the centric heterochromatin of chromosoaime 2 is markedly different from that found in euchromatin The interchromosomal effect is absent here, whereas heat induces an increase roughly an order of magnitude greater than that found in euchromatin and totally unlike the lack of response in the proximal heterochromatin of the X chromosome It is proposed that the sequestering of DNA satellite I (thermal dissociation 9–20° lower than that of the other major satellites) in the centromeric heterochromatin of chromosome 2 (but not in X or 3) may account for the increase

Journal ArticleDOI
TL;DR: The chromosomes of uncultured cells of the near-diploid mouse plasmacytoma MOPC-31C were studied and a common breakpoint in chromosome "15 at band D3/E" was found and is considered of possible importance in the development of this tumor.
Abstract: The chromosomes of uncultured cells of the near-diploid mouse plasmacytoma MOPC-31C were studied. The modal number of chromosomes was 44. The tumor lacked two marker chromosomes, reciprocal translocation [rcp t(12; 15)], that in previous studies were found to be common to 3 other uncultured myelomas and 1 cultured mouse myeloma. Through the formation of two markers, rcp t(6; 15), unique to this tumor, however, the tumor shared with other tumors and their specific markers a common breakpoint in chromosome "15 at band D3/E. This breakpoint has been found in all mouse plasmacytomas examined with banding thus far and is considered of possible importance in the development of this tumor.

Journal ArticleDOI
TL;DR: Chromosomes from four patients with variants of the Turner syndrome were investigated by G- and C-bandind and DNA replication techniques, and replication patterns of normal early- and late-replicating X chromosomes were studied in two normal females.
Abstract: Chromosomes from four patients with variants of the Turner syndrome were investigated by G- and C- banding and DNA replication techniques. Their karyotypes were: 1) 46,X,idic(X)(q28), 2) 45,X/46,X,idic(X)(q24), 3)45,X/ 46,X,idic(X)(p11), and 4) 46,X,i(Xq). In Patients 1, 2, and 3, the abnormal X was isodicentric, with different break-and-fusion points in each case. In each, the G-band pattern on one side of the breakpoint was a mirror image of that on the other side. Each had two distinct C-bands, only one of which was associated with a primary constriction. The fourth patient had an isochromosome of the long arm of an X in which only one C-band could be discerned. Replication studies were done on lymphocyte cultures by incorporating a thymidine analogue and staining with acridine orange. In addition, replication patterns of normal early- and late-replicating X chromosomes were studied in two normal females. In the four patients, all the normal X chromosomes had normal early-replication patterns. The two idic(X) chromosomes with break-and-fusion points on their long arms almost always had symmetric replication patterns, which demonstrates that the corresponding bands replicated synchronously. In contrast, many of the idic(X)(p11) and i(Xq) chromosomes showed asymmetric or asynchronous replication. In each, the replication pattern of the abnormal X was similar to the equivalent portions of a normal late-replicating X.

Journal ArticleDOI
TL;DR: The authors discuss the clinical and cytogenetic problems raised in two new cases of X-chromosome translocations involving a child who presented marked growth retardation, behavioral anomalies, and discrete facial malformations at age 3 months.
Abstract: The authors discuss the clinical and cytogenetic problems raised in two new cases of X-chromosome translocations.

Journal ArticleDOI
TL;DR: X-linked enzymes were compared in oocytes of XX and XO fetal mice and HPRT shows a large increase in enzyme activity during early meiotic stages, while G6PD does not, and places the time of X reactivation at the entry to meiosis.