The location of the gene for haemophilia

Summary Sirks' theory that the gene for haemophilia can cross over between the X and Y chromosomes is critically examined. The cross-over frequency must be of the order of one in ten thousand. Some difficulties in the theory are pointed out, and methods by which it may be tested are discussed.     

A complex sex-chromosome system in the hare-wallaby Lagorchestes conspicillatus Gould

Among specimens of the spectacled hare-wallaby Lagorchestes conspicillatus Gould (Marsupialia, family Macropodidae) 4 males had 15 chromosomes and 2 females 16 chromosomes. The sex chromosomes are X₁X₁X₂X₂ in the female and X₁X₂Y in the male, the Y being metacentric and both X chromosomes are acrocentric. In about 96% of sperm mother cells at meiosis the sex chromosomes form a chain trivalent and in more than 99% of these this orients convergently so that the X₁ and X₂ move to the same pole. Evidence is presented that L. conspicillatus has evolved from a form with 22 chromosomes including a small X and a minute Y. Autoradiographic studies show that the proximal fifth of the X₁ chromosome replicates late. This is probably the ancestral X chromosome which has been translocated to an autosome. The fate of the original Y is obscure but an hypothesis is proposed that it forms the centromeric region of the Y. A single male had 14 chromosomes and was heterozygous for a translocation involving the centric fusion of two acrocentric autosomes. In about 30% of sperm mother cells the autosomal trivalent did not disjoin regularly but, despite this, all secondary spermatocytes observed at metaphase 2 had balanced complements of chromosomes. It is assumed that unbalanced secondary spermatocytes died before reaching metaphase.     

Des lignées apocaryogamiques et leur ségrégation dans la population de l'Acrosiphonia arcta,Chlorophycée marine d'Héligoland

Resume 1. La caryogamie est supprimée dans des zygotes obtenus à partir d'une souche sauvage unialgale de l'Acrosiphonia arcta (Dillw.)J. Ag. de Héligoland.2. Les deux pronucléi des pseudozygotes ainsi formés peuvent se séparer définitivement au moment de la première segmentation de l'élément zygotique qui intervient au bout d'une quinzaine de jours.3. Les pseudozygotes se développment directement en nouvelles plantes d'Acrosiphonia.4. Les plantes issues de pseudozygotes ainsi que les plantes-mères possèdent des noyaux haploïdes avec n=5 chromosomes.5. L'Acrosiphonia arcta d'origine apocaryogamique semble constituer des lignées micto-haploïdes stables et génétiquement isolées. Leur origine et leur mode de ségrégation sont discutés.

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Apocaryogamic strains and their segregation in the population of the marine chlorophyceanAcrosiphonia arcta from Helgoland

Nuclear studies of zygotes obtained from the wild type ofAcrosiphonia arcta (Dillw.)J. Ag. from Helgoland were carried out in order to test the hypothesis that these algae might be of apocaryogamic origin. It is shown that caryogamy may be completely suppressed in zygotes of this species, although plasmogamy is normally carried out. The two pronuclei which do not fuse, become definitively separated after the first segmentation of zygote. In culture, these zygotes develop directly into filamentous plants which are morphologically similar to those from which they originate. These plants possess haploid nuclei with n=5 chromosomes. The same chromosome number is found in the mother plants. Since successive generations continue to reproduce by apocaryogamy, it is suggested that genetically isolated micto-haploid strains occur in theA. arcta population studied. Origin and segregation of such strains are discussed.

     

The chromosomes of Dall's porpoise,Phocoenoides dallii (True), with remarks on the phylogenetic relation of the Cetacea

Summary The chromosome complex of Dall's porpoise Phocoenoides dallii (True), a species of the Delphinidae (Cetacea), was investigated in male germ cells during the course of spermatogenesis. The diploid number of chromosomes in this species was 44 in the spermatogonia and the haploid number was 22 in both primary and secondary spermatocytes. Sex chromosomes of the typical XY-type were found to occur in this species. The X element is represented by one of the medium-sized chromosomes of rod-type characterized by a globular body located at its inner extremity, while the Y is very minute, attaining a size approximately one third that of the smallest autosome.Morphological analysis of the chromosomes shows the chromosome complement of this species to be strikingly characterized by the prevalence of medium-sized elements having subterminal fibre attachments. Comparison of the chromosomes with those of related forms of mammals shows that the chromosome constitution of this species approximates closely that of the pig. The question of the phylogenetical affinity of the Cetacea was discussed on the basis of the karyological evidence here reported.Contribution No. 213 form the Zoological Institute, Faculty of Science, Hokkaido University, Sapporo, Japan.     

Reversion of XO to XY sex chromosome mechanism in a phasmid

Summary The sex chromosomes of the male phasmid Isagoras schraderi Rehn comprise an X and a Y, — each with a submedian kinetochore, and one euchromatic and one heterochromatic arm. At meiosis X and Y form an unequal sex bivalent in which the euchromatic arms are terminally associated. Relatively recent reversion from the XO-XX mechanism characteristic of the Phasmidae is indicated by the presence of the euchromatic arm in both X and Y. The diploid number of the male is 34.Unequal autosomal bivalents are found at meiosis in two other species of Isagoras — Isagoras subaquiles Rehn and Isagoras sp. — and in Pseudophasma menius Westwood. The chromosome complements of these species are described.     

Homoeologous relationship between wheat and rye chromosomes. Present status

The work on methods for determining the homoeologous relationship between wheat and rye chromosomes has been reviewed. The results obtained for rye chromosomes belonging to different homoeologous groups have been discussed. It is proposed that chromosome 3R of Lee et al. (1969) should be designated as 1R/3R. It is pointed out that homoeology of all seven rye chromosomes may not be known in the future also, due to translocations. It is, therefore, suggested that Secale montanum should be used instead of S. cereale. Future lines of work have been suggested.     

DNS-Reduplikationsmuster der Somatischen Chromosomen von Cricetus cricetus (L.)

The patterns of terminal DNA synthesis of the autosomes and sex chromosomes of Cricetus cricetus were studied. Characteristic late replicating segments are found on all chromosomes allowing identification of most autosomes. The sex chromosomes of both sexes behave similarly; in the male, half of the X and the entire Y are late replicating and heteropycnotic, in the female, half of one X and the whole of the other X. The isopycnotic part of the X-chromosome comprises about 5% of the haploid female complement.

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Wesentliche Teile der vorliegenden Arbeit werden von Fräulein Dorothee Hepp als Dissertation der Medizinischen Fakultät der Universität Freiburg i. Br. vorgelegt.

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Wir danken Dr. Susumu Ohno für kristiche des Munuskriptes und Fräulein Elke Faisst für ihre bei den experimentellen Arbeiten.     

Fundamentally different repetitive element composition of sex chromosomes in Rumex acetosa

Background and AimsDioecious species with well-established sex chromosomes are rare in the plant kingdom. Most sex chromosomes increase in size but no comprehensive analysis of the kind of sequences that drive this expansion has been presented. Here we analyse sex chromosome structure in common sorrel (Rumex acetosa), a dioecious plant with XY₁Y₂ sex determination, and we provide the first chromosome-specific repeatome analysis for a plant species possessing sex chromosomes.MethodsWe flow-sorted and separately sequenced sex chromosomes and autosomes in R. acetosa using the two-dimensional fluorescence in situ hybridization in suspension (FISHIS) method and Illumina sequencing. We identified and quantified individual repeats using RepeatExplorer, Tandem Repeat Finder and the Tandem Repeats Analysis Program. We employed fluorescence in situ hybridization (FISH) to analyse the chromosomal localization of satellites and transposons.Key ResultsWe identified a number of novel satellites, which have, in a fashion similar to previously known satellites, significantly expanded on the Y chromosome but not as much on the X or on autosomes. Additionally, the size increase of Y chromosomes is caused by non-long terminal repeat (LTR) and LTR retrotransposons, while only the latter contribute to the enlargement of the X chromosome. However, the X chromosome is populated by different LTR retrotransposon lineages than those on Y chromosomes.ConclusionsThe X and Y chromosomes have significantly diverged in terms of repeat composition. The lack of recombination probably contributed to the expansion of diverse satellites and microsatellites and faster fixation of newly inserted transposable elements (TEs) on the Y chromosomes. In addition, the X and Y chromosomes, despite similar total counts of TEs, differ significantly in the representation of individual TE lineages, which indicates that transposons proliferate preferentially in either the paternal or the maternal lineage.     

Analysis of two 47,XXX males reveals X-Y interchange and maternal or paternal nondisjunction

Summary Two cases of 47,XXX males were studied, one of which has been published previously (Bigozzi et al. 1980). Analysis of X-linked restriction fragment length polymorphisms revealed that in this case, one X chromosome was of paternal and two were of maternal origin, whereas in the other case, two X chromosomes were of paternal and one of maternal origin. Southern blot analysis with Y-specific DNA probes demonstrated the presence of Y short arm sequences in both XXX males. In one case, the results obtained pointed to a paracentric inversion on Yp of the patient's father. In situ hybridization indicated that the Y-specific DNA sequences were localized on Xp22.3 in one of the three X chromosomes in both cases. The presence of Y DNA had no effect on random X inactivation. It is concluded that both XXX males originate from aberrant X-Y interchange during paternal meiosis, with coincident nondisjunction of the X chromosome during maternal meiosis in case 1, and during paternal meiosis II in case 2.     

Endothelial microvilli in the vessels of the rat gasserian ganglion and testis

Summary In the Gasserian ganglion and testis of the rat the endothelium of the small blood vessels has a singular appearance due to the presence of a high number of microvillous processes. These arise from the luminal surface, either individually, or in small groups. The significance of this structure is not known. It is pointed out that these vessels are particularly sensitive to cadmium intoxication.This investigation was performed during a tenure by Dr. Gabbiani of a fellowship of the Medical Research Council of Canada and was supported by the National Institutes of Health (Grant No. 5R01 HE-08794-04) and the Ministère de la Santé du Québec (projet 604-7-635).The authors wish to thank Dr. S. M. Shea for his advice in the measurement of the villi. The technical assistance of Miss Virginia Gilmore and of Mr. Eduardo Garriga is gratefully acknowledged.     

Characterization of the human Xq21.3/Yp11 homology block and conservation of organization in primates

The Xq21.3/Yp11 homology block on the human sex chromosomes represents a recent addition to the Y chromosome through a transposition event. It is believed that this transfer of material occurred after the divergence of the hominid lineage from other great apes. In this paper we investigate the structure and evolution of the block through fluorescence in situ hybridisation, contig assembly, the polymerase chain reaction, exon trapping, sequence comparison, and annotation of sequence data. The overall structure is well conserved between the human X chromosome and the Y chromosome as well as between the X chromosomes from different primates. Although the sequence data reveal a high level of nucleotide sequence identity for the human X and Y, there are regions of significant divergence, such as that around the marker DXS214. These are presumably the consequence of multiple rearrangements during evolution and are of particular importance with respect to the potential gene content in this segment of the interval.     

Pseudodicentric 22;Y translocation transmitted through four generations of a large family without phenotypic repercussion

The most frequent Y-autosome translocations involve an acrocentric autosome and they are frequently familial with neither phenotypic nor reproductive repercussion. However, different Y-autosome translocations have been related to infertility, due to abnormal pairing of the X and Y chromosomes at meiosis and an abnormal XY-body formation or by the disruption of the AZFs (Azoospermic Factor). Rare forms of Y-autosome translocations are those resulting in an unbalanced 45-chromosome karyotype that includes a dicentric Y+autosome chromosome. We describe a new case of a familial pseudodicentric 22;Y that is carried by 19 male members of a large family without phenotypic repercussion. Cytogenetic analysis, fluorescence in situ hybridisation (FISH) and subtelomeric Multiplex Ligation-dependent Probe Amplification (MLPA) assay have been performed. All male members of the family showed the karyotype 45,X,psu dic(22;Y)(p11.2;qter).ish psu dic(22;Y) (SRY+,DYZ3+,D14/D22Z1+). In conclusion, the presence of the dicentric chromosome in the male members of the family reported does not seem to interfere with the correct progression of spermatogenesis.     

The meiotic chromosomes of man

Summary Information was obtained on the chromosome number, and the behavior of autosomes as well as of the sex chromosomes in meiosis in human male germ cells derived from 25 Japanese patients, 4 to 79 years in age, who were hospitalized mostly due to epididymitis, prostate cancer, undescended testes or infertility.In 16 out of the 25 specimens, the chromosome numbers, 46 in 2n and 23 in n, were consistently established together with an XY sex-determining mechanism based on spermatogonial and spermatocyte divisions. No reliable counts were obtained from the remaining 9 cases, because of that they provided no cells for precise investigation.The X and Y chromosomes during the leptotene stage were observed as two separate heteropycnotic bodies lying along the inner wall of the nucleus, while at pachytene they formed a sex-vesicle after homologous pairing. At the diplotene, diakinesis and first metaphase the X and the Y appeared as an isopycnotic bivalent showing an end-to-end association, though there were some cells in which they remained as two separate entities free from contact. Evidence was presented that the X and the Y seemed to associate with each other at the distal end of the short arm of each element.One or sometimes two smallest autosomal bivalents tended to show rather precociously a chiasma-terminalization at the first metaphase.The metaphase chromosomes of the second spermatocytes were evident by the haploid number as well as by their widely diverged chromatids with a characteristic spiral configuration.The testicular materials under study contained in most cases polyploid cells with a considerable frequency in spermatogonia as well as in first and second spermatocytes. Giant sperm heads were observed not infrequently, mostly being abnormal in shape. No significant correlation was obtained between the frequency of polyploid cells and the age of patients so far studied.Contribution No. 679 from the Zoological Institute, Faculty of Science, Hokkaido University, Sapporo. — It is our pleasure to dedicate this paper to Professor Dr. Hans Bauer, Max-Planck-Institut für Meeresbiologie, Tübingen, in honor of his sixtieth birthday.     

Répartition des chromosomes humains au stade métaphase de la division cellulaire

Résumé 33 caryotypes masculins et 17 caryotypes féminins ont été étudiés quant à la distribution de chromosomes des groupes A, B et G dans les mitoses au stade métaphase de la division cellulaire.

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Distribution of human chromosomes [1 and 3 (groupe A), 4 and 5 (group B) and 21 and 22 (group G) + the Y chromosome] in metaphase figures of leucocyte division

Summary The object of this paper is to study the distribution of chromosomes in the metaphase figures of human leucocytes cultures. We studied, in the group A, the chromosomes 1 and 3, easily recognisable; in the group B: the chromosomes 4 and 5 and in the group G: the chromosomes 21, 22 and the sex chromosome Y.The method we used consits in calculating the real distance of the centomer of a chromosome to the center of the figure.We compared one distribution to the other and we submitted our results to some statistical tests.It appears clearly that chromosomes are not randomly distributed in metaphase figures of human leucocytes.

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Ce travail a été subventionné par le Fonds de la recherche médicale     

Über die Bedeutung der Diminution von Ascaris Megalocephala

Summary Great theoretical value has always been attached toBoveri's discovery as regards chromatin diminution inAscaris, for this discovery appeared to expose the mechanism causing the propagative cells, in which all chromatin remains, to originate an entirely new organism, whereas the soma cells of which the chromosomes have been diminished are only capable of specific differentiation.Boveri was further able to show that, not only do the soma and propagative nuclei differ from each other, but that rather the character of the cell-plasma decides whether the nucleus diminishes or not. Considerations are brought forward to prove that the diminisher hypothesis as given byKing andBeams, is untenable. Diminution has always been supposed to result in the loss of the totipotence of the diminished nuclei. In the light of recent chromosome research this course of events does not seem probable. Therefore the following theory is brought forward: When the egg ofAscaris is split, blastomeres originate, which differ from each other as to the plasma. In proportion to the quality of the surrounding plasma, now these now other genes of the totipotent nucleus react in different cells, thus originating the specific differentiation of the cell in question. This cooperation between plasma and nucleus is, however, at first obstructed in the large collective chromosomes ofAscaris, by the presence of their thickened ends. In order to keep up this cooperation a certain quality of plasma is needed, situated in a certain horizontal zone of the egg. As soon as, in the course of the division, nuclei come to rest in different zones, a diminution occurs, and differentiation of the cells in question sets in. Towards the end of the embryonic development the ends of the chromosomes are lost in the propagative cells, and also in these cells differentiation occurs.

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Résumé On a toujours attribué une haute signification théorique à la découverte deBoveri, de la diminution des chromatines chez l'ascaris puisqu'elle semblait expliquer le mécanisme qui cause que les cellules propagatrices où séjourne, la totalité de l'effectif des chromatines, font de nouveau sortir d'elles-mêmes un organisme entier, pendant que les cellules somatiques, dont les chromosomes ont été diminués, ne sont plus capables qu'à produire une différenciation spécifique. De plus,Boveri a pu démontrer, que les noyaux somatiques et propagateurs ne sont pas, à peu de chose près, différents, mais que c'est bien plus la qualité du plasme des cellules qui décide si les noyaux qui leur ont été distribués, diminuent ou non. Des arguments sont apportés, qui démontrent que l'hypothèse du diminisher échafaudée parKing etBeams est insoutenable. En général on s'est représenté. l'action de la diminution de telle façon que la totipotentialité des noyaux diminués a été perdue. Cependant, le fait n'est pas acceptable quand on le considère à la lumière de la recherche moderne sur les chromosomes. Par conséquent, nous proposons l'opinion suivante: Dans l'uf de l'ascaris, des blastomères différant plasmatiquement les uns des autres prennent naissance pendant le fendage. Selon l'état du plasme environnant, dans les cellules individuelles on voit réagir certain gène, dans les autres un autre gène du noyau totipotentiel, causant ainsi la différenciation des cellules visées. Cette collaboration entre le plasme et le noyau est cependant premièrement bloquée dans les grands chromosomes collectifs de l'ascaris par la présence des bouts de chromosomes épaissis. Pour leur conservation une certaine qualité de plasme est requise qui se trouve dans une zone horizontale déterminée de l'uf. Dès que, dans le procès du fendage, des noyaux arrivent dans d'autres zones du plasme, la diminution a lieu, et la différenciation des cellules visées s'opère. Cependant, après la conclusion du développement embryonal, les bouts des chromosomes se perdent dans les cellules propagatrices et la différenciation a lieu aussi dans ces cellules.

     

SEX REVERSAL: A FOUNTAIN OF YOUTH FOR SEX CHROMOSOMES?

Nonrecombining Y chromosomes are expected to degenerate through the progressive accumulation of deleterious mutations. In lower vertebrates, however, most species display homomorphic sex chromosomes. To address this, paradox I propose a role for sex reversal, which occasionally occurs in ectotherms due to the general dependence of physiological processes on temperature. Because sex‐specific recombination patterns depend on phenotypic, rather than genotypic sex, homomorphic X and Y chromosomes are expected to recombine in sex‐reversed females. These rare events should generate bursts of new Y haplotypes, which will be quickly sorted out by natural or sexual selection. By counteracting Muller's ratchet, this regular purge should prevent the evolutionary decay of Y chromosomes. I review empirical data supporting this suggestion, and propose further investigations for testing it.     

Chromosomal divergence and evolutionary inferences in Rhodniini based on the chromosomal location of ribosomal genes

In this study, we used fluorescence in situ hybridisation to determine the chromosomal location of 45S rDNA clusters in 10 species of the tribe Rhodniini (Hemiptera: Reduviidae: Triatominae). The results showed striking inter and intraspecific variability, with the location of the rDNA clusters restricted to sex chromosomes with two patterns: either on one (X chromosome) or both sex chromosomes (X and Y chromosomes). This variation occurs within a genus that has an unchanging diploid chromosome number (2n = 22, including 20 autosomes and 2 sex chromosomes) and a similar chromosome size and genomic DNA content, reflecting a genome dynamic not revealed by these chromosome traits. The rDNA variation in closely related species and the intraspecific polymorphism in Rhodnius ecuadoriensis suggested that the chromosomal position of rDNA clusters might be a useful marker to identify recently diverged species or populations. We discuss the ancestral position of ribosomal genes in the tribe Rhodniini and the possible mechanisms involved in the variation of the rDNA clusters, including the loss of rDNA loci on the Y chromosome, transposition and ectopic pairing. The last two processes involve chromosomal exchanges between both sex chromosomes, in contrast to the widely accepted idea that the achiasmatic sex chromosomes of Heteroptera do not interchange sequences.     

Sex chromosome pairing patterns in male mice of novel Sxr genotypes

The influence of the sex-reversal factor (Sxr) on X and Y chromosome pairing was examined by comparing males with novel and standard Sxr genotypes. The novel Sxr males were exceptional in carrying Sxr on their X rather than their Y chromosome, or homozygously on both their X and Y chromosomes, or on a Y chromosome of different origin to that on which the factor arose. Regardless of its chromosomal location, Sxr was found to elevate the frequency of X-Y separation. Univalent X and Y chromosomes were observed to undergo self-association in a variable proportion of spermatocytes of all Sxr-carrying males. There was a suggestion that chromosomal location of the factor could influence the frequency of univalent self-association. Our observations do not support the published hypothesis of Y self-pairing as the cause of the elevated rate of X-Y separation at pachytene in Sxr-carrying males. Rather, they suggest that heterozygosity due to the presence of Sxr in the XY pairing region may be sufficient to disrupt pairing and cause univalence, or alternatively, that Sxr is an inefficient promoter of X-Y pairing initiation.     

Asynchronie intra- et interchromosomique de l'incorporation de la thymidine 3H dans les chromosomes d'Haemanthus katharinae Bak

Résumé Chez Haemanthus katharinae Bak. il y à une paire des chromosomes longs contenant deux régions qui incorporent intensément de la thymidine ³H après la replication de l'ADN le long de tout le chromosome. Les chromosomes courts terminent la synthèse de l'ADN plus tôt que les chromosomes longs. Dans les chromosomes courts, à l'étape finale de la synthèse de l'ADN, l'incorporation arrive uniquement aux environs des centromeres.     

Localization of the ribosomal RNA genes in Drosophila simulans

In situ hybridization of cloned rRNA genes from Drosophila melanogaster to D. simulans metaphase chromosomes shows that in the tested wild type strains both sex chromosomes contain a nucleolus organizer region. Silver grain counts support the published data that the X chromosomal rRNA gene number is significantly higher than the Y chromosomal.