Showing papers on "X chromosome published in 1968"
TL;DR: The autoradiographic behavior of normal male and female chromosomes in blood leukocytes at various stages in the DNA synthesis period (S period) has been investigated with 3H-thymidine and the time sequence and pattern of chromosomal replication in normal human leukocyte is delineated.
Abstract: The autoradiographic behavior of normal male and female chromosomes in blood leukocytes at various stages in the DNA synthesis period (S period) has been investigated with 3H-thymidine. One X chromosome in female cells and the Y in male cells do not replicate their DNA or do so to a limited extent, 12 h before metaphase, when most of the other chromosomes are undergoing replication at a substantial rate. Asynchrony among the chromosomes is evident at that time. Furthermore, the X in female cells and the Y in male cells are the last chromosomes to finish their DNA replication. The replication of an elongated No. 1 autosome in a patient with primary amenorrhea has been compared to that of its normal homolog. The secondary constriction area, particularly prominent in the elongated No. 1, is the last area to finish replication in both the abnormal and normal No. 1 autosomes and is one of the latest segments in the human complement to finish replication. The leukocyte generation time was found to be 18 h or more in the presence of phytohemagglutinin (PHA). The data presented further delineate the time sequence and pattern of chromosomal replication in normal human leukocytes.
72 citations
TL;DR: One mammalian X chromosome in females and the Y chromosome in males are heterochromatic, and they seem to carry “controlling centers” which affect both sex determination and various somatic characters.
Abstract: One mammalian X chromosome in females and the Y chromosome in males are heterochromatic, and they seem to carry “controlling centers” which affect both sex determination and various somatic characters. The euchromatic X chromosome may carry the structural genes for testicular as well as ovarian determination, the former only functioning in the presence of a Y chromosome or suitable autosomal modifier.
72 citations
TL;DR: Information about the chronology of DNA replication in structurally abnormal X chromosomes is relevant to the study of the genetic activity of mammalian sex chromosomes as well as for two mammalian species, mouse and man.
Abstract: THE Lyon hypothesis1 was constructed on genetical evidence derived from observations of sex-linked variegation of coat colour in the mouse. Within the framework of this hypothesis, late DNA synthesis and genetic inactivity of the same X chromosome are considered strictly related phenomena. Thus information about the chronology of DNA replication in structurally abnormal X chromosomes is relevant to the study of the genetic activity of mammalian sex chromosomes. So far, such information is available only for two mammalian species, mouse and man. In human females, structurally abnormal X chromosomes, such as deficiencies, duplication/deficiencies or rings, were found to be consistently late-replicating compared with the normal X chromosome2. The same applies to a presumptive X-autosome translocation3. In the mouse, two cases of X-autosome translocations have been studied cytogenetically, with contrasting results. In females heterozygous for Searle's translocation (T16H), in which part of the X chromosome is translocated on to an unidentified autosome, the sex-linked variegation is suppressed. Lyon et al.4, by the appropriate genetic tests, showed that the translocated X was consistently active while the normal X was inactive in all cells. Ohno and Lyon5 later reported that the normal X of heterozygous females carrying the translocation showed positive heteropycnosis in 90 per cent of somatic prophases.
38 citations
TL;DR: In phenotypic males with a 47,XYY sex-chromosome constitution the mean testosterone output was significantly higher than in normal ambulant males, but was not significantly different from that in inpatient controls with a 46,XY constitution.
38 citations
TL;DR: It is concluded that the X chromosome's reorientation response is the critical factor in non-random segregation in Gryllotalpa.
Abstract: Males of Gryllotalpa hexadactyla have 22 autosomes and one X chromosome in their chromosome complement. One pair of autosomes forms a heteromorphic bivalent in meiosis: one dyad is several times the size of the other. At metaphase of the first meiotic division the large dyad and the X chromosome are invariably oriented to the same pole, and they move to this pole in anaphase. These earlier observations (Payne, White) have been confirmed by studies on living spermatocytes, and a preliminary experimental analysis by micromanipulation has been made. No physical connection between the X chromosome and the heteromorphic bivalent could be detected when either one was moved with a microneedle. When the X chromosome was detached from the spindle in prometaphase and brought to the other pole, it oriented to this pole, but it usually reoriented and moved back to the original pole. When the heteromorphic bivalent was detached from the spindle and its position inverted, the large and the small dyads oriented to the new poles. The heteromorph remained in inverted position but the X chromosome usually reoriented and moved to the pole to which the large dyad was now oriented. When the heteromorph was detached and taken out of the cell, the X chromosome reoriented and moved to the other pole, reoriented again and moved back to the original pole. When the X chromosome was detached and taken out of the cell the heteromorph did not show any reaction. It is concluded that the X chromosome's reorientation response is the critical factor in non-random segregation in Gryllotalpa.
30 citations
TL;DR: The development of techniques for the quantita-tive analysis of the parental source of the X chromosomes in series of patients with XO and XXY karyotypes created a need for a parti- cular type of family data to test the theoretical framework against observable data.
Abstract: The development of techniques for the quantitative analysis of the parental source of the X chromosomes in series of patients with XO and XXY karyotypes (Fraser, 1963) created a need for a particular type of family data to test the theoretical framework against observable data. Patients with the syndromes of Turner and Klinefelter are not easy to identify and study in appreciable numbers in any locality outside the great metropolitan centres. This is due to the relative rarity of Turner's syndrome and the even greater rarity of karyotypically confirmed diagnoses of both these syndromes. Studies of the parents and sibs of such patients are difficult because some patients are in institutions, many are adults, and their close relatives may be dispersed or deceased. Thus the material presented in this report is not large but may be useful if pooled with similar data from other areas. Reviews dealing with the area of genetic interest of this study and summarizing the earlier reports have been those of Lindsten (1963), McKusick (1964), Miller (1964), and Hambert (1966).
26 citations
01 Jan 1968
TL;DR: Preliminary observations described suggest that, in the nucleus of the female, sex chromatin formation resulting from the condensation of an X chromosome at interphase is not directly related to the mitotic cycle but may berelated to the metabolic state of the cell.
Abstract: The aim of this study is to determine why, in contrast to expectations based on the Lyon hypothesis, a variable number of nuclei of cells from mammalian females are sex chromatin negative. The frequency of sex chromatin positive nuclei was determined in cell cultures of varying cell densities. The cells were derived from seven chromosomally normal human female embryos, one newborn female with an extra E group chromosome and two normal male embryos. In all cultures of females the frequency of sex chromatin positive nuclei increased linearly from about 35% to 60% at cell densities of less than one cell per 0.01 mm2 of culture surface to 90% to 100% at densities of 20 to 125 cells per 0.01 mm2. This frequency-to-density relationship was independent of the mitotic rate and the rate at which cell density increased. When large variations in cell density were produced intentionally on the same glass coverslip, sex chromatin frequency was related to the density of cells in any one area of a coverslip and seemed to be largely independent of the cell density in other parts of the coverslip. The frequency of sex-chromatin-like bodies of male cultures remained very low at all cell densities. These and other preliminary observations described suggest that, in the nucleus of the female, sex chromatin formation resulting from the condensation of an X chromosome at interphase is not directly related to the mitotic cycle but may be related to the metabolic state of the cell.
26 citations
TL;DR: The chromosomes of the reindeer (2n = 70) were studied with special reference to the chronology of DNA replication of the sex chromosomes.
Abstract: The chromosomes of the reindeer (2n = 70) were studied with special reference to the chronology of DNA replication of the sex chromosomes. The X chromosome was metacentric and nearly of the duplicate
23 citations
TL;DR: Two members of theArtiodactyla, the African sitatunga and the Indian blackbuck, have now been found to have this peculiarity of extra large sex chromosomes, and theories concerning the formation of these outsized chromosomes are discussed.
Abstract: Sex chromosomes in mammals are generally of the XY type with the X chromosome constituting 5% by weight of the haploid chromosomal complement. Unusually large sex chromosomes have been described in a few species all of which belong to theRodentia, but two members of theArtiodactyla, the African sitatunga and the Indian blackbuck, have now been found to have this peculiarity. The sitatunga has an X chromosome that represents 13.08% and a Y that represents 7.29% of the haploid complement, and the X of the blackbuck represents 14.96% of its haploid complement. Portions of both extra large sex chromosomes in a pair are late replicating. Theories concerning the formation of these outsized chromosomes are discussed.
21 citations
TL;DR: This experiment was designed to investigate the replicative behaviour of the X chromosomes in the bovine (Bos taurus) female complement at various times during the DNA synthetic period with the hope of finding an explanation for the discrepancy.
Abstract: Further Evidence for the Simultaneous Initiation of DNA Replication in both X Chromosomes of Bovine Female
21 citations
TL;DR: A new case of ratio distortion in the house mouse is found in which an elemenit acting in segregation and recombination like a mutant gene greatly reduces the probability of its own transmission through sperm, although it is transmitted normally through eggs.
Abstract: Genietically controlled distortions of the normal proportions of functiolnal gametes from heterozygotes are occasionally detected as departures from Mendelian rules. Few well-analyzed cases of this kind have been reported in animals. We have recently found a new case of ratio distortion in the house mouse in which an elemenit acting in segregation and recombination like a mutant gene greatly reduces the probability of its own transmission through sperm, although it is transmitted normally through eggs. In this preliminary paper, we will report the results of breeding experiments that establish the above diagnosis, and the outcome of the first tests of two hypotheses concerning the mechanism by which the effect is produced. In the few cases of this kind analyzed in insects and mammals, the aberrations are also confined, as in our new case, to proportions of male gametes. In Drosophila pseudoobscura, males with a mutation known as "sex-ratio" in the X chromosome produce chiefly daughters since the mutation causes the Y chromosome to be lost in spermatogenesis so that chiefly X-bearing sperm are formed. ' In Drosophila melanogaster, a mutation in the second chromosome, knowit as segregation distorter (SD), causes the SD-bearing chromosome to be tralnsmitted by males to most of the offspring, up to more than 99 per cent. The exact mechanism is not known, but it appears to involve interference by SD with the production or function of normal sperm containing the homologue of the SD chromosome. 2 3 In the house mouse, a series of mutant alleles (t-alleles) in one region of the ninth linkage group has been identified; in many cases the mutant allele, usually lethal or semilethal, is transmitted by heterozygous males to a great majority (80-99%) of the offspring. The same alleles are transmitted in normal proportions by female heterozygotes.4 Certain t-alleles that are fully viable when homozygous are transmitted by heterozygous males in low ratios, as is the case with the factor to be described. The mechanism in most of these cases is not established but in one case may involve effects of the mutant allele on sperm function after meiosis.5,6 The niew factor that we have found in the mouse is referred to as "Low ratio" (Lr). We have been able to follow its transmission through some 9 or 10 generations because of its linkage with a dominant marker T (Brachy or short tail) in the ninth linkage group. When Lr occurs in the same chromosome with T (T Lr/+-+), it causes T to be transmitted by males to about 14 per cent of the offspring. Complete results for the first five generations are shown in Table 1. Daughters receiving T and Lr from. their father transmit T to their progeny in normal ratios (0.5). Brachy (T Lr) sons of these daughters again transmit T to about 14 per cent of their off spring (Table 1).
TL;DR: Two cases of partial deletion of the long arm of the X chromosome are reported and DNA replication studies revealed that the partially deleted X chromosome was predominantly late replicating.
TL;DR: It is realized that the existence in a parent of a balanced translocation can result in an abnormal child as the result of a chromosome abnormality other than an unbalanced translocation.
Abstract: IT HAS become standard practice to study the chromosomes of parents of children with Down's syndrome before giving genetic counseling. In some families the presence of a balanced translocation greatly increases the risk of having another similarly affected child. The chance of an unbalanced karyotype and, therefore, an affected individual can be estimated from the normal segregation ratios. Before giving counseling, however, it is important to realize that the existence in a parent of a balanced translocation can result in an abnormal child as the result of a chromosome abnormality other than an unbalanced translocation. In phenotypically normal individuals balanced translocations can at times interfere with meiosis in such a way as to cause nondisjunction.1-4The resulting offspring carry the balanced translocation and, in addition, are trisomic for another chromosome,2-4or in the case of the X chromosome, they are monosomic.1We are reporting our findings in
Journal Article•
TL;DR: Reports of a translocation of the Y chromosome to an autosome are even rarer than those involving the X chromosome, and the cases described by Federman et al 9 and van den Berghe 10 are the only two in which a recognizable amount of a Y chromosome was thought to be.
Abstract: ALTHOUGH a great variety of autosomal translocations have been described in man (Thompson 1 ), little is known about the translocations between a sex chromosome and an autosome. A translocation which involves both an X chromosome and an autosome has been well documented in the mouse, 2-4 but has not been well established in man, although there have been a few reports of presumptive cases. 5-7 Recently Neuhauser and Back 8 reported the case of a girl with multiple malformations with a possible translocation between one of the C-group autosomes and an X chromosome; they based their interpretation on the karyotype and the deoxyribonucleic acid replication patterns. Reports of a translocation of the Y chromosome to an autosome are even rarer than those involving the X chromosome. The cases described by Federman et al 9 and van den Berghe 10 are the only two in which a recognizable amount of a Y chromosome was thought to be
TL;DR: Autoradiographic studies indicate that the two morphologically distinguishable X chromosomes are out-of-phase in DNA replication in approximately equal proportion and thus substantiate the random inactivation hypothesis.
Abstract: The karyotype ofTatera indica cuverii consists of 68 chromosomes with two X chromosomes in the female and an X and a Y chromosome in the male. The X chromosomes are the largest and can be distinguished from each other morphologically. Autoradiographic studies indicate that the two morphologically distinguishable X chromosomes are out-of-phase in DNA replication in approximately equal proportion and thus substantiate the random inactivation hypothesis.
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TL;DR: A curious imbalance appears to occur in nature, the possession of two X chromosomes by one sex (usually the female) compared with only one X in the other sex as discussed by the authors, where most such genes produce the same effect in both sexes.
Abstract: A curious imbalance appears to occur in nature—the possession of two X chromosomes by one sex (usually the female) compared with only one X in the other sex. Thus, all genes on the X in the female are present in a double dose when compared with the male. Yet most such genes produce the same effect in both sexes. An intriguing theory to account for this equalization of expression has recently been proposed, and the investigation should enhance our comprehension of X chromosome aberrations, sex differences, and the basic mechanisms of gene action in the developing embryo and the maturing organism.
01 Jan 1968
TL;DR: It is concluded that the polymorphism is a result of deletion and duplication of the short arm, so that the karyotypes presented here should be considered normal.
Abstract: Only the two largest pairs of autosomes and the X chromosome are individually identifiable. Pairing of all other autosomes and identification of the Y are arbitrary. In females, one entire X and possibly the short arm of the second X are late replicating. Several teams of investigators have found that the short arm of the largest subtelocentric autosomes is polymorphic. It may be completely absent, a single, knob-like structure (as shown here), or two such structures with a secondary constriction separating these two components. Cohen and Pinsky, from their breeding studies, concluded that the polymorphism is a result of deletion and duplication of the short arm, so that the karyotypes presented here should be considered normal.
Journal Article•
TL;DR: It was found that if 5 µCi/ml.
Abstract: ONE X chromosome of the human female lymphocyte has been shown to synthesize DNA later than do its homologue and other chromosomes of the complement1–3 Attempts by us to demonstrate a similar replication pattern for chromosomal protein have been unsuccessful4 In this study, cultures were exposed to 1 µCi/ml only of 3H-arginine or 3H-lysine for the 4–6 h previous to chromosome preparation It was found, however, if 5 µCi/ml of 3H-arginine were used, a large chromosome of the 6-X-12 group seemed to be synthesizing protein later than was the rest of the complement (Fig 1)
01 Jan 1968
TL;DR: Skin cultures of two animals from the Catskill Game Farm were initiated for karyological studies and the X chromosome was identified by H3-thymidine radioautography in the female as one late replicating element.
Abstract: Skin cultures of two animals from the Catskill Game Farm were initiated for karyological studies. The results are identical with the karyotypes constructed from lymphocyte cultures by Tietz and Teal. The X chromosome was identified by H3-thymidine radioautography in the female as one late replicating element.
TL;DR: La morphologie du chromosomeX pendant prophase I dans le mâle de Saimiri boliviensis, Macaca mulatta, Galago demidovii andTarsius syrichta suggère l'existence des synapses dan le chromosomeX des mammifères due to the possible existence d'une duplication dans ce chromosome.
Abstract: La morphologie du chromosomeX pendant prophase I dans le mâle deSaimiri boliviensis, Macaca mulatta, Galago demidovii etTarsius syrichta suggere l'existence des synapses dans le chromosomeX des mammiferes due a la possible existence d'une duplication dans ce chromosome.
01 Jan 1968
TL;DR: From karyotypes of a large number of specimens, representing several subspecies, no variation (except the Y chromosome) was found, and because of the similarity of many chromosome pairs and the lack of distinct morphological grouping, minor variations in karyotype among subspecies may exist but are difficult to detect.
Abstract: The X chromosome is the most outstanding element of the entire complement, but determination of the Y is somewhat equivocal, since several pairs of autosomes have similar morphology. From karyotypes of a large number of specimens, representing several subspecies, no variation (except the Y chromosome) was found. In some individuals, the Y chromosome may be smaller than the one presented here. However, because of the similarity of many chromosome pairs and the lack of distinct morphological grouping, minor variations in karyotype among subspecies may exist but are difficult to detect.
TL;DR: The temporal relation and correlation between the syntheses of DNA and protein of bovine female sex chromosomes were studied and no X chromosome was found to be late labeling with respect to protein containing either 3H-lysine or3H-arginine.
Abstract: The temporal relation and correlation between the syntheses of DNA and protein of bovine female sex chromosomes were studied. Significant differences were found between the patterns of protein and DNA synthesis as studied by 3H-lysine and 3H-arginine incorporation into protein and 3H-thymidine incorporation into DNA. In contrast to the late-labeling X chromosome for DNA, no X chromosome was found to be late labeling with respect to protein containing either 3H-lysine or 3H-arginine. No distinct differences were found between the patterns of incorporation of the two tritiated amino acids into the chromosome protein.
01 Jan 1968
TL;DR: In females, the two X chromosomes may differ in morphology, one being more metacentric than the other, presumably the result of differential heteropycnotic behavior.
Abstract: Identification of the X chromosome is unequivocal. In females, the two X chromosomes may differ in morphology, one being more metacentric than the other, presumably the result of differential heteropycnotic behavior.
01 Jan 1968
TL;DR: The Y chromosome is indistinguishable from the two pairs of the smallest telocentric autosomes, but identification of the X chromosome is unequivocal.
Abstract: The Y chromosome is indistinguishable from the two pairs of the smallest telocentric autosomes, but identification of the X chromosome is unequivocal.