Showing papers on "X chromosome published in 1977"
TL;DR: It is concluded that the parental origin of X m and X p marks them as different from one another, and possible causes for the failure of the expression of X p in the yolk sac endoderm and the tissue specificity of the effect are discussed.
318 citations
TL;DR: In man, the specific chromosome that carries each of about 210 gene loci is known as mentioned in this paper, including at least one assigned to each chromosome (including the Y), about 110 assigned to specific autosomes, and about 100 to the X chromosome.
Abstract: In man, the specific chromosome that carries each of about 210 gene loci is known. These loci include at least one assigned to each chromosome (including the Y), about 110 assigned to specific autosomes, and about 100 to the X chromosome. For many loci, information on regional chromosomal localization is also available. The information comes mainly from studies in families and somatic cell hybrids, as well as an intgratsight of results from the two methods. Knowledge of the chromosome map gives insight into evolution, chromosomal organization in relation to genetic control mechanisms, and the pathogenesis of neoplasms and malformations. Furthermore, it is useful in prenatal or premorbid diagnosis of hereditary diseases.
301 citations
TL;DR: An X-linked pattern of transmission observed in four families with familial mental retardation in several generations was associated with a probable secondary constriction at the distal end of the q arms of the X chromosome.
Abstract: An X-linked pattern of transmission observed in four families with familial mental retardation in several generations was associated with a probable secondary constriction at the distal end of the q arms of the X chromosome. Twenty retarded males and no retarded females were observed. All available live retarded males and most of their normal mothers were found to have the abnormal X chromosome. The marker chromosome was shown to be the X chromosome in each case by Giemsa banding. In affected male and female carriers the marker chromosome varied in appearance and was not present in all metaphases. The significance of this study in relation to previously reported pedigrees showing non-specific X-linked mental retardation is discussed.
166 citations
TL;DR: A gene order of Hq-Ta-Pgk-1-Mo is suggested, based on recombination data, which shows that males from feral sampling or from a variety of genetic crosses have only a single-banded phenotype of the variant PGK-1A type or of thePGK- 1B type commonly found among inbred mice.
Abstract: Electrophoretic variation for X-chromosome-linked phosphoglycerate kinase (PGK-1) has been found as a polymorphism in feral mice in Denmark. Males from feral sampling or from a variety of genetic crosses have only a single-banded phenotype of the variant PGK-1A type or of the PGK-1B type commonly found among inbred mice. By contrast, three phenotypes were observed among females; two homozygous single-banded types and a heterozygous double-banded type. The X-chromosome linkage of the Pgk-1 locus was determined from the mode of inheritance in F1 and backcross generations and confirmed by the linkage of Pgk-1 and the X-linked markers Hq, Ta and Mo. Pgk-1 showed 29/122 recombinations with Hq, 5/185 with Ta and 0/108 recombinants with Mo. Based on these recombination data, a gene order of Hq—Ta—Pgk-1—Mo is suggested.
114 citations
TL;DR: The balance of the aneuploidy was characterized by chromosome loss and the involvement of all chromosome groups, and was consistent with chromosome loss from metaphase cells damaged during preparation for cytogenetic examination.
Abstract: In PHA-cultured lymphocytes, about 8% of metaphases from 32 women were aneuploid compared to 4% of metaphases from 35 men A significant part of this aneuploidy was characterized by sex chromosome involvement: in women, the loss or gain of X chromosomes; in men, the gain of X chromosomes and the loss or gain of Y chromosomes The incidence of this aneuploidy was positively age-related for both sexes Premature division of the X-chromosome centromere was closely associated with X-chromosome aneuploidy in women and men, and appeared to be the mechanism of nondisjunction causing this aneuploidy Premature centromere division (PCD) indicated a dysfunction of the X-chromosome centromere with aging, and this dysfunction was the basic cause of age-related aneuploidy A similar mechanism of nondisjunction may operate for the Y chromosome of men, but could not be clearly demonstrated because of the low incidence of Y-chromosome aneuploidy
114 citations
TL;DR: Analysis of hybrids obtained by virus-induced fusion of hamster cells with irradiated human cells permits a study of the effects of lethal doses of radiation on human cells and provides a method of sub-chromosomal genetic mapping that is independent of karyological analysis.
Abstract: Hybrid cells were obtained by virus-induced fusion of hamster cells with irradiated human cells. The analysis of such hybrids permits a study of the effects of lethal doses of radiation on human cells and provides a method of sub-chromosomal genetic mapping that is independent of karyological analysis. Radiation-induced chromosome exchanges are shown to be extremely localized, and a map of 4 X-linked genes is presented.
97 citations
TL;DR: The findings substantiate the existence of Duchenne dystrophy manifesting in females with normal karyotypes and readily explained by lyonization of the X-chromosome after twinning has occurred.
Abstract: Duchenne muscular dystrophy manifested in one of girl twins. The twins were monozygous on the basis of red cell and HL antigens and skin graft compatibility. Karyotyping, including banding techniques, showed a normal number of chromosomes and a normal conflguration of the X-chromosome in both twins. The twins were identical in appearance until symptoms of Duchenne dystrophy developed in one at age-4.years. The maternal uncle had classic Duchenne dystrophy; the mother and the nonmanifesting twin showed evidence of being heterozygous for Duchenne dystrophy. The phenotypic difference in monozygous twins is readily explained by lyonization of the X-chromosome after twinning has occurred. The findings substantiate the existence of Duchenne dystrophy manifesting in females with normal karyotypes.
94 citations
TL;DR: This family and the other eleven cases of Xp- fertile women found in the literature demonstrate that loss of the p21 → pter region of the X chromosome is compatible with fertility, probably because it leaves on Xp the region which is never inactivated.
Abstract: A woman balanced carrier of a X/15 translocation gave birth to a balanced infertile son and three unbalanced Xp- fertile daughters. This family and the other eleven cases of Xp- fertile women found in the literature demonstrate that loss of the p21 → pter region of the X chromosome is compatible with fertility, probably because it leaves on Xp the region which is never inactivated.
86 citations
TL;DR: Three X/autosomal translocations, two familial and one de novo, were analyzed, resulting for these patients in a partial trisomy of 17q, and their peculiar phenotype is described.
Abstract: Three X/autosomal translocations, two familial and one de novo, were analyzed. Late-replicating chromosomes and chromosome regions were studied with R-banding techniques after BrdU incorporation. The first translocation, t(X;4)(q21;q13), was a de novo translocation, found in a woman with amenorrhea. The structurally normal X was late replicating in all cells. The second translocation, t(X;6)(p21;q26), was found in an unbalanced form, 46,XX,der(6), in a phenotypically abnormal girl; her mother carried the balanced translocation. In the mother's blood culture inactivation of the X's followed two modes: In 85% of the cells the normal X was late replicating, and in the remaining 15% the der(X) was inactivated, including the attached fragment of chromosome 6. The third translocation, t(X;17)(p11;q24), was found in three generations. In the phenotypically normal mother, who carried the balanced translocation, the late-replicating X was always the normal X. In her daughters, who had an unbalanced karyotype, 46,X,der(X), and multiple congenital abnormalities, the X part of the translocation chromosome was always late replicating. No spreading of inactivation over the attached autosomal region was observed, resulting for these patients in a partial trisomy of 17q. Their peculiar phenotype is described.
85 citations
TL;DR: The structural gene Sgs-4 responsible for larval saliva protein 4 of Drosophila melanogaster was localized, with the help of Notch deficiencies, within the section between bands 3C10 and 3D1 of the X chromosome.
Abstract: The structural gene Sgs-4 responsible for larval saliva protein 4 of Drosophila melanogaster was localized, with the help of Notch deficiencies, within the section between bands 3C10 and 3D1 of the X chromosome. In this chromosome section there is, very probably, only one fine band. In the third larval instar chromosome this section is transcriptionally active and forms a puff. When the ecdysone concentration increases, about 5 h before prepupa formation, it becomes inactive. — In section 3C of X chromosomes of third instar larvae of the stock Hikone-R no puff is formed. The saliva of these larvae lacks protein 4. However, female hybrids (H/B and H/O) from Hikone-R crossed with Berlin and Oregon respectively produce a Hikone-specific saliva protein 4h. The synthesis of protein 4h in the hybrids H/B and H/O is ascribed to an activation of the gene Sgs-4 in the Hikone chromosome. — In the saliva of heterozygotes (FM1/H) carrying one inversion chromosome In(1) FM1 and one X chromosome from Hikone, protein 4h could not be detected. In these inversion heterozygotes in 90% of all nuclei the homologues are not paired in 3C, and 3C is puffed only in the FM1 chromosome. This suggests that a precondition for the activation of Hikone gene Sgs-4 in heterozygotes may be intimate homologue pairing. — Intersexes with one of their X chromosomes from Hikone-R and the other from Berlin produce relatively more protein 4h than do diploid H/B females, indicating facilitated transcription as a result of dosage compensation.
78 citations
TL;DR: The present observations lend indirect support to the working hypothesis, the assumption that interference with X-chromosome inactivation is a possible cause of spermatogenic breakdown in carriers of various male-sterile chromosomal transloations.
Abstract: A new meiotic phenomenon is described in male mice heterozygous for the male-sterile translocations T(10;13)199H, T(16;17)43H, and T(7;19)145H. The phenomenon consists of a nonrandom contact between the C bands of the X chromosome and the translocation configuration in diakinesis/metaphase I plates. Translocation configurations with positively heteropycnotic regions, often associated with the allocyclic X chromosome, are found in some early diakineses that have not been overtreated with alkali. Such heteropycnosis of a part of translocated autosome, apparently in phase with the allocyclic X, is typical for all three male-sterile translocations. In contrast to these findings, neither nonrandom contacts nor positive heteropycnosis of the translocation configuration can be found in males heterozygous for the translocation T(9;17)138Ca, which does not impair spermatogenesis. Dissociation of the X and Y at diakinesis is significantly enhanced in sterile males, though the occurrence of dissociation is evidently not related to the presence of the C-band contact between translocated chromosomes and the X. A working hypothesis is proposed, relating the observed nonrandom C-band contact and heteropycnosis of translocated chromosomes to a presumed impairment of X inactivation in primary spermatocytes and to consequent failure of spermatogenesis. An alternative explanation cannot be excluded, however, which would account for the hitherto available data without postulating any causal relationship between the meiotic findings and male sterility. Both alternatives are amenable to experimental verification.
TL;DR: While axis formation and migration of the axes along the plane of the nuclear envelope proceed normally in the X and Y chromosomes, true synapsis does not occur because the pairing region of the X chromosome has probably been relocated far from the chromosome termini by the insertion of distal C-heterochromatic blocks.
Abstract: The behavior of the X and Y chromosomes in somatic and testicular cells of the sand rat (P. obesus) has been investigated with light and electron-microscope procedures. The Y chromosome has been identified as the fourth longest of the complement, both by C-banding and by its meiotic behavior. The X chromosome is the longest of the complement and carries two major C-heterochromatic blocks, one in the distal part of the long arm and the other forming most of the short arm. During presynaptic stages in spermatocytes, separate C-heterochromatic blocks, representing the sex chromosomes, are observed in the nuclei. An XY body is regularly formed at pachytene. During first meiotic metaphase the X and Y chromosomes show variable associations, none of them chiasmatic. Second meiotic metaphases contain, as in other mammals, a single sex chromosome, suggesting normal segregation between the X and the Y. — Electron microscopic observations of the autosomal synaptonemal complexes (SCs) and the single axes of the X and Y chromosomes during pachytene permit accurate, statistically significant identification of each of the largest chromosomes of the complement and determination of the mean arm ratios of the X and Y axes. The X and Y axes always lie close to each other but do not form a SC. The ends of the X and Y axes are attached to the nuclear envelope and associate with each other in variable ways, both autologously (X with X or Y with Y) and heterologously (X with Y), with a tendency to form a maximum number (four) of associated ends. Analysis of 36 XY pairs showed no significant preference for any single specific attachment between arm ends. The eighth longest autosomal bivalent is frequently partially asynaptic during early pachytene, and only at that time is often near or touching one end of the X axis. — It is concluded that while axis formation and migration of the axes along the plane of the nuclear envelope proceed normally in the X and Y chromosomes, true synapsis (with SC formation) does not occur because the pairing region of the X chromosome has probably been relocated far from the chromosome termini by the insertion of distal C-heterochromatic blocks.
TL;DR: Results suggest a preferential transcription of ribosomal DNA from the D. melanogaster genome when nucleolus organizers from both species are present in conjunction, a phenomenon termed nucleolar dominance.
TL;DR: DNA replication kinetics in late X chromosomes from amniotic fluid cells and skin fibroblasts are strikingly different from those observed in lymphocytes with respect both to the initiation and termination of DNA synthesis, consistent with the existence of tissue-specific influences on the control of DNA replication in human X chromosomes.
Abstract: Regional DNA replication kinetics in human X chromosomes have been analysed using BrdU-33258 Hoechst-Giemsa techniques in five cell types from human females: amniotic fluid cells, fetal and adult skin fibroblasts, and fetal and adult peripheral lymphocytes. In all cell types, the late-replicating X chromosome can be distinguished from its active, earlyreplicating homologue, and both the early and late X exhibit temporally and regionally characteristic internal sequences of DNA replication. The replication pattern of the early X in amniotic fluid cells and skin fibroblasts is similar to that of the early X in lymphocytes, although certain discrete regions are later-replicating in these monolayer tissue culture cells than are the corresponding regions in lymphocytes. However, DNA replication kinetics in late X chromosomes from amniotic fluid cells and skin fibroblasts are strikingly different from those observed in lymphocytes with respect both to the initiation and termination of DNA synthesis. The predominant late X pattern observed in 80–95% of lymphocytes, in which replication terminates in the long arm in bands Xq21 and Xq23, was never seen in amniotic fluid cells or skin fibroblasts. Instead, in these cell types, bands Xq25 and Xq27 are the last to complete DNA synthesis, while bands Xq21 and Xq23 are earlier-replicating; this pattern is similar to the alternative replication sequence observed in 5–20% of lymphocyte late X chromosomes. This replication sequence heterogeneity is consistent with the existence of tissue-specific influences on the control of DNA replication in human X chromosomes.
TL;DR: The results provide the first direct evidence for the assignment of the HPRTlocus to the X chromosome in Chinese hamster, and in fact allow mapping of this locus to the distal region of the short arm.
Abstract: The phenomenon of segregation of gene expression has been examined in intraspecific somatic cell hybrids. Specifically, segregation at the hypoxanthine guanine phosphoribosyltransferase (HPRT)locus has been studied in hybrids of Chinese hamster cell lines. The role of chromosome segregation, or other chromosomal events has been assessed by detailed comparison of karyotypes in the 6-thioguanine resistant segregants with those of the parental hybrid lines. The results clearly demonstrate that loss of an entire X chromosome is the primary event responsible for segregation at the HPRTlocus, while deletion of a portion of the short arm of an X chromosome was also a frequent event. The results provide the first direct evidence for the assignment of the HPRTlocus to the X chromosome in Chinese hamster, and in fact allow mapping of this locus to the distal region of the short arm. Analysis of chromosome number distributions in the hybrids and segregants suggests that in selecting chromosomal segregants one may also select for hybrid lines with reduced chromosome stability.
Journal Article•
TL;DR: Tests with five isozyme markers and two coat color genes have tentatively ruled out linkage of DMH susceptibility on seven autosomes and the 47% tumor incidence among 57 male resistant backcross hybrids, regardless of whether their single X chromosome was inherited from the ICR/Ha or C57BL/Ha strain, provides evidence against sex linkage.
Abstract: Genetic analysis of colon tumor induction by symmetrical 1,2-dimethylhydrazine (DMH) was undertaken in F1, F2, and reciprocal backcross hybrids derived from a cross between two inbred mouse strains, the 100% susceptible ICR/Ha and completely resistant C57BL/Ha. Mice, 12 to 14 weeks old, received 22 successive weekly s.c. injections of 0.35% aqueous solution of DMH buffered to pH 6.5. A dose of 15 mg/kg/mouse/week produced invasive colon adenocarcinomas in all ICR/Ha males and females (60 of 60) within 22 weeks. None of the 90 C57BL/Ha mice developed DMH tumors during 44 weeks of observation. Susceptibility to the carcinogen was dominant, as indicated by 100% colon tumor incidence in reciprocal ICR/Ha X C57BL/HaF1 hybrids (68 of 68) and in the susceptible backcross ICR/Ha X F1 (42 of 42). Tumor yield in F2 hybrids (94 of 120) was 78%, which is in close agreement with the 3:1 ratio expected if a single dominant DMH susceptibility gene is inherited via the F1 from the ICR/Ha grandparent. Likewise, tumor yield in resistant backcross mice of genotype C57BL/Ha X F1 (46 of 117) is not out of line with the anticipated 1:1 ratio in the latter type of test hybrids. Tests with five isozyme markers and two coat color genes have tentatively ruled out linkage of DMH susceptibility on seven autosomes. The 47% tumor incidence among 57 male resistant backcross hybrids, regardless of whether their single X chromosome was inherited from the ICR/Ha or C57BL/Ha strain, provides evidence against sex linkage.
TL;DR: Denatured 3H-labelled DNAs containing histone gene sequences originating from the echinoderms Psammechinus miliaris, Echimus esculentus and Strongylocentrotus purpuratus have been in situ hybridized to RNA transcripts on newt lampbrush chromosomes.
Abstract: Denatured 3H-labelled DNAs containing histone gene sequences originating from the echinoderms Psammechinus miliaris, Echimus esculentus and Strongylocentrotus purpuratus have been in situ hybridized to RNA transcripts on newt lampbrush chromosomes. Autoradiographs of the hybridized lampbrush preparations show labelling restricted to four or fewer lateral loop pairs all lying within the heteromorphic regions of chromosome I, also one or two loop pairs on chromosome VI, one loop pair on chromosome X and one loop pair on chromosome XI. For oocytes from a single newt, coincident label distribution is found with DNA's of diverse echinoderm origin; however different newts show some specific individual diversity in label distribution, including heterozygosity in the case of loops on bivalents VI and X. The more conspicuously labelled loops, particularly those on chromosome I, show a pattern of labelling which is explicable if the newt histone DNA sequences are confined to short intercepts of lateral loop axis. Transcription is initiated prior to the histone DNA sequences, proceeds through the histone DNA sequences, and beyond, and the histone RNA sequences are cut from the transcripts before the termination of transcription.
TL;DR: A human-mouse hybrid, DUR 4 (Solomon et al., 1976), containing a human X/15 translocation chromosome and also chromosome 5, among other human chromosomes, was used in a double selection system to obtain hybrids of four different types.
Abstract: A human-mouse hybrid, DUR 4 (Solomon et al., 1976), containing a human X/15 translocation chromosome and also chromosome 5, among other human chromosomes, was used in a double selection system to obtain hybrids of four different types: X/15+ 5+, X/15– 5+, X/15+ 5, and X/15– 5–. Standard positive and negative selection systems were used for the X chromosome, and negative selection for chromosome 5 was done with diphtheria toxin. The assignment of HEXB and the diphtheria toxin sensitivity gene to chromosome 5 was confirmed. HEXA was present only when both the X/15 chromosome and chromosome 5 were present. A “HEXA-like” band segregated with chromosome 15 (or X/15) but independently of chromosome 5. This component, unlike HEXA, does not contain human HEXβ antigen.
TL;DR: The expression of another X-linked enzyme, α-galactosidase, is examined and a 300-fold increase in activity is reported, probably due to the expression of embryonic X chromosomes, during preimplantation development.
Abstract: THE most widely accepted model for X-chromosome dosage compensation in female mammals is the single-active X hypothesis (Lyon hypothesis)1. X-Chromosome dosage compensation probably occurs at about the time of implantation of the embryo into the uterus2,3 but it is not known whether this arises by a process of X-chromosome inactivation or by X-chromosome activation4. There is now good evidence for the expression of the embryonic genome during preimplantation development5–10 and Lyon2,3 has reviewed the evidence suggesting that X chromosomes are also expressed during this period. This includes both indirect observations11–13 and the more direct experiments with the X-linked enzyme hypoxanthine guanine phosphoribosyl-transferase (HPRT) (ref. 10). We have examined the expression of another X-linked enzyme, α-galactosidase14–15 and report here a 300-fold increase in activity during preimplantation development. This is probably due to the expression of embryonic X chromosomes.
TL;DR: Evidence is obtained against the implication that two functional X chromosomes are required for the onset of mammalian meiosis, which is not supported by evidence that XO mice produce normal gametes.
Abstract: THERE is considerable evidence that, as a result of some early embryonic event, the genes of one X chromosome in each somatic cell of the human female are not expressed1. Studies of somatic tissues and cultured cells (including fibroblast clones) from human embryos, heterozygous for the common electrophoretic variant of glucose-6-phosphate dehydrogenase (G6PD), indicate that a single active X is present in cells from various tissues, at least by 5 weeks from conception2. On the other hand, the presence of the heteropolymorphic form of the enzyme in oocytes of the heterozygous adult female3 and a 16-week-old foetus4 is compelling evidence that, in meiotic stage germ cells, there are two active X chromosomes; however, the basis for the two active chromosomes in oocytes is not clear. It is conceivable that germ cell progenitors escape inactivation because inactivation occurs when cells destined to become germ cells have already been imprinted. Alternatively, only a single X chromosome may be active in all cells of the early zygote, with the second X activated only in germ cells at some time after their differentiation. The third possibility, that germ cells are subject to inactivation, but that reactivation occurs when meiosis commences, has been suggested by Gartler et al. because they did not observe the heteropolymer in ovaries from a 12-week-old human foetus heterozygous for the G6PD variant5,6. The ovary at that developmental stage contains approximately 23% germ cells, with a preponderance of premeiotic and leptotene germ cells7. But the implication that two functional X chromosomes are required for the onset of mammalian meiosis is not supported by evidence that XO mice produce normal gametes8. Using human foetal material, we have now obtained evidence against the third possibility.
TL;DR: It is found that there is no support in either female or male meiosis for the concept that satellite DNA is involved in meiotic chromosome pairing of either a chiasmate or an achiasmate kind.
Abstract: We have examined the female meiotic behaviour of three X chromosomes which have large deletions of the basal heterochromatin in Drosophila melanogaster. We find that most of this heterochromatin can be removed without substantially altering pairing and segregation of the two Xs. To compare the role of heterochromatin in male meiosis we have constructed individuals which carry two extra identical heterochromatic mini X chromosomes. These minis behave as univalents even though their heterochromatin is known to contain satellite DNA. We conclude therefore that this satellite DNA is not sufficient to allow effectively normal meiotic behaviour. In all other respects our results in the male extend and confirm Cooper's postulate that there exist specific pairing sites in the X heterochromatin. Thus we find no support in either female or male meiosis for the concept that satellite DNA is involved in meiotic chromosome pairing of either a chiasmate or an achiasmate kind.
TL;DR: Two further cases (one previously published as D/D translocation) of 15/15 translocation in Prader-Willi syndrome are reported, which brings the total cases of this specific chromosomal anomaly in connection with this specific syndrome up to three or possibly four.
Abstract: Two further cases (one previously published as D/D translocation) of 15/15 translocation in Prader-Willi syndrome are reported, which brings the total cases of this specific chromosomal anomaly in connection with this specific syndrome up to three or possibly four. It is suggested that Prader-Willi syndrome might be caused by loss of short arm material of chromosome 15.
TL;DR: The behavior of meiotic chromosomes during spermatogenesis suggests that the karyotype of these species has evolved from a karyotypes analogous to that of Strongyloides ratti with 2 pairs of autosomes and a pair of X chromosomes.
Abstract: Parasitic females of Strongyloides ransomi and Strongyloides papillosus have 4 chromosomes and reproduce exclusively by mitotic (apomictic) parthenogenesis. The free-living generation includes females and males. The females have 2 pairs of chromosomes of unequal size and reproduce by meiotic parthenogenesis following obligatory pseudofertilization (gynogenesis). The males undergo spermatogenesis by the regular meiotic process and have the same chromosomal complement as the females. During prophase I, however, a portion of one homologue of the large bivalent breaks free and subsequently is diminished, as in S. ransomi, or it rejoins the original homologue, as in S. papillosus. This behavior of meiotic chromosomes during spermatogenesis suggests that the karyotype of these species has evolved from a karyotype analogous to that of Strongyloides ratti with 2 pairs of autosomes and a pair of X chromosomes, following fusion of the X chromosome with an autosome and the formation of a Neo-X and a Neo-Y chromosome. The female karyotype of S. ransomi and S. papillosus thus may be 2A + 2 Neo-X. The males are phenotypic males and have the same karyotype as the females, but their functional karyotype may be 2A + Neo-X + Neo-Y.
TL;DR: Data is reported which shows that in fibroblast cells cultured from tissue explants of these two species the paternally derived allele is also weakly expressed, suggesting the possibility of a form of mosaicism as in eutherians but with unequal proportions of the two types of cell.
Abstract: The locus for the glycolytic enzyme phosphoglycerate kinase A (PGK-A) is sex-linked in the eastern grey kangaroo (M. giganteus) and the pretty-face or whip tail wallaby (M. parryi). Females older than the pouch life stage of development do not express their paternally derived allele in some tissues such as blood and liver. This phenomenon is called paternal X inactivation and is characteristic of kangaroos. This distinguishes them from eutherian females, which are mosaics of two kinds of cell brought about by random X inactivation of either the paternally derived or the maternally derived X chromosome. But in skeletal and cardiac muscle the paternally derived allele is weakly expressed. This paper reports data which show that in fibroblast cells cultured from tissue explants of these two species the paternally derived allele is also weakly expressed. This suggests the possibility of a form of mosaicism as in eutherians but with unequal proportions of the two types of cell. Our results show this is not so. Cloning experiments have been performed with cultured cells from three heterozygous M. giganteus females. A total of 49 clones was obtained and each clone was like its parent culture, i.e. there was a strongly active maternally derived allozyme and a weak paternally derived one. Two interpretations of these data are possible. Each cell may have a fully active maternally derived allele and a partly active paternally derived one. Or the clones themselves may be heterogeneous, such that one or the other of the X-linked alleles may switch on or off every few cell generations or less. Since X inactivation is known to be rather stable this latter hypothesis is considered the less likely. Autoradiography shows that the longer arm of the X chromosome in the cultured cells is late-replicating. Thus later replication of the X chromosome in kangaroos does not necessarily mean complete inactivity. Differences in morphology between the two X chromosomes in females are described.
TL;DR: A study of patients with sex chromosome aneuploidy supports the view that taurodontism, a rare anomaly of the pulp chamber, is related to the presence of additional X-chromosomes, but it cannot be considered an obligatory part of the Klinefelter (XXY) syndrome.
TL;DR: A 32‐year‐old man was found to have seminoma of the right testis which had been subjected to orchiopexy for cryptorchism 14 years earlier, which is the first reported case of seminoma associated with Klinefelter's syndrome.
Abstract: A 32-year-old man was found to have seminoma of the right testis which had been subjected to orchiopexy for cryptorchism 14 years earlier. The left testis was small and firm, and the patient was further studied for hypogonadism. Chromosome analysis revealed a karyotype of 47, XXY, 15s+ with an extra X chromosome and enlarged and fluorescent satellites on chromosome 15. The satellites were also found in the mother as well as in two sisters and one brother out of his four siblings. Endocrine studies, histological pictures of the biopsied left testis and dermatoglyphic analysis were compatible with Klinefelter's syndrome. To our knowledge this is the first reported case of seminoma associated with the syndrome. Several implications are discussed for the rare occurrence of a germinal cell tumor in Klinefelter's syndrome.
TL;DR: The frequency of sister chromatid exchanges (SCEs) induced by mitomycin C (MMC) in Indian Muntjac chromosomes was determined by the fluorescence plus Giemsa (FPG) technique and a threshold effect for the induction of SCEs was observed in regions resistant to DNA extraction by acid and alkali treatments.
Abstract: The frequency of sister chromatid exchanges (SCEs) induced by mitomycin C (MMC) in Indian Muntjac chromosomes was determined by the fluorescence plus Giemsa (FPG) technique. Using scanning cytophotometry the relative DNA content of each chromosome was measured with and without acid or alkali pretreatments for C-banding. During acid and alkali treatments, euchromatin lost 20 to 30% of its DNA, while heterochromatin lost less than 5%; an intermediate DNA loss was observed for the short arm of the X chromosome. After growth of cells in the presence of MMC during the first cycle and in the presence of bromodeoxyuridine (BrdU) during the first and second cycles of DNA replication, SCEs in the euchromatin were proportional to DNA content. SCEs at the junctions between the neck of the X chromosome and the long and short arms occurred more frequently than expected. A threshold effect for the induction of SCEs was observed in regions resistant to DNA extraction by acid and alkali treatments (i.e., the neck and short arm of the X chromosome). At high concentrations of MMC, the frequency of SCE at each junction appears to plateau at 0.5.
TL;DR: Evidence will be provided to suggest an extension of the minimal limits of the "critical region" in the long arm of the X chromosome from A-B, as described by Sarto and associates, to new minimal limits C-D.
TL;DR: The combined data emphasise the clinical and genetic heterogeneity of the disorder and show that in at least some instances a heritable component may be the primary insult.
Abstract: The genetic, clinical, and necropsy findings of 2 brothers with the prune belly anomaly are presented and the literature reviewed. The combined data emphasise the clinical and genetic heterogeneity of the disorder and show that in at least some instances a heritable component may be the primary insult. The most likely heritable explanation involves a two-step autosomal dominant mutation with sex-limited expression that partially mimics X-linkage.