INTRASPECIES AUTOSOMAL POLYMORPHISM AND CHROMOSOME REPLICATION IN AKODON MOLINAE (RODENTIA: CRICETIDAE)

1969 ◽  
Vol 11 (2) ◽  
pp. 233-242 ◽  
Author(s):  
N. O. Bianchi ◽  
J. Contreras ◽  
F. N. Dulout
Keyword(s):  
Bone Marrow ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Chromosome Analysis ◽  
Chromosome Replication ◽  
Chromosome 1 ◽  
Submetacentric Chromosome ◽  
Sex Chromatin ◽  
S Period

Cell spreads from bone marrow, spleen, testis and liver of four male and four female Akodon molinae (Rodentia:Cricetidae) were used for chromosome analysis and sex chromatin scoring. Chromosome replication at the beginning and end of the S period were analysed in bone marrow cells.In five animals (three males and two females) the diploid chromosome number was 42; the other three (1 male and 2 females) had a modal number of 43. In the former animals pairs 1,2,19,20 and the Y chromosome were easily identified morphologically. Chromosomes 1 were large and metacentric. In specimens with 43 chromosomes, pairs 2-20-XY were similar to those of animals with 42. Instead of having two number 1 homologues, these animals showed three unpaired chromosomes, one chromosome 1, one subterminal chromosome (1a) homologue of the long arm of the chromosome 1 and one submetacentric chromosome (1b) homologue of the short arm of the chromosome 1 Chromosomes 1a and 1b were considered to have arisen by a Robertsonian mechanism of centric fission of chromosome 1 plus a pericentric inversion.Studies of sex chromosome replication showed that the Y chromosome was the last to start and to end DNA synthesis in male complements. In females one X chromosome was the last to start replication. No late replicating X chromosome at the end of the S period was found. Coincidently, no sex chromatin could be detected in females.Analysis of late replication patterns in chromosomes 1, 1a and 1b, indicates that pericentric inversions can shift the replicating moment of the chromosomal regions involved in the rearrangement.

scholarly journals A second X chromosome contributes to resilience in a mouse model of Alzheimer’s disease

2020 ◽  
Vol 12 (558) ◽  
pp. eaaz5677 ◽  
Author(s):  
Emily J. Davis ◽  
Lauren Broestl ◽  
Samira Abdulai-Saiku ◽  
Kurtresha Worden ◽  
Luke W. Bonham ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Testicular Development ◽  
X Chromosomes ◽  
Model Of Alzheimer’S Disease ◽  
Preclinical Ad ◽  
Brain Expression

A major sex difference in Alzheimer’s disease (AD) is that men with the disease die earlier than do women. In aging and preclinical AD, men also show more cognitive deficits. Here, we show that the X chromosome affects AD-related vulnerability in mice expressing the human amyloid precursor protein (hAPP), a model of AD. XY-hAPP mice genetically modified to develop testicles or ovaries showed worse mortality and deficits than did XX-hAPP mice with either gonad, indicating a sex chromosome effect. To dissect whether the absence of a second X chromosome or the presence of a Y chromosome conferred a disadvantage on male mice, we varied sex chromosome dosage. With or without a Y chromosome, hAPP mice with one X chromosome showed worse mortality and deficits than did those with two X chromosomes. Thus, adding a second X chromosome conferred resilience to XY males and XO females. In addition, the Y chromosome, its sex-determining region Y gene (Sry), or testicular development modified mortality in hAPP mice with one X chromosome such that XY males with testicles survived longer than did XY or XO females with ovaries. Furthermore, a second X chromosome conferred resilience potentially through the candidate gene Kdm6a, which does not undergo X-linked inactivation. In humans, genetic variation in KDM6A was linked to higher brain expression and associated with less cognitive decline in aging and preclinical AD, suggesting its relevance to human brain health. Our study suggests a potential role for sex chromosomes in modulating disease vulnerability related to AD.

scholarly journals True hermaphroditism associated with microphthalmia

1999 ◽  
pp. 62-65 ◽  
Author(s):  
T Hayashi ◽  
Y Kageyama ◽  
K Ishizaka ◽  
T Tsujii ◽  
H Oshima
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Inguinal Canal ◽  
Chromosome Analysis ◽  
Interstitial Deletion ◽  
Seminiferous Tubules ◽  
Left Testis ◽  
Primordial Follicles ◽  
The Right ◽  
Hormonal Condition

A 4-year-old boy with an undescending left testis, penoscrotal hypospadia and bilateral microphthalmia was admitted to our hospital. Chromosome analysis revealed a karyotype of 46, XX del(x)(p2 2,31) and the sex-determining region of the Y chromosome (SRY) was negative. The right testis was located in the scrotum and a left cystic ovary-like gonad, a salpinx and a unicorn uterus were found in the left inguinal canal. Histologically the gonad was an ovotestis in which primordial follicles covered infantile seminiferous tubules. Microphthalmia is observed in some congenital syndromes caused by interstitial deletion of the X chromosome. This case suggested that the short arm of the X chromosome was involved in the differentiation of the gonad. Very closely located follicles and infantile seminiferous tubules indicated that induction of meiosis in the fetus was controlled by the local microenvironment in follicles and seminiferous tubules, and not by the systemic hormonal condition.

scholarly journals XXY Mice

1961 ◽  
Vol 2 (1) ◽  
pp. 156-158 ◽  
Author(s):  
Bruce M. Cattanach
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Mouse Testis ◽  
Chromosome Counts ◽  
Cleavage Division ◽  
Chromosomal Constitution ◽  
Sister Chromatids

Welshons & Russell (1959) have presented data to show that the XO chromosomal constitution in the mouse is female. This conclusion was based on results of genetical tests with sex-linked markers and on chromosome counts. All XO females were matroclinous, that is, they had inherited their X-chromosome from their mother. Females of this type will arise when non-disjunction occurs in the meiotic divisions of the father and results in spermatozoa without a sex-chromosome. Alternatively, the paternal sex-chromosome may be lost from the fertilized ovum if non-disjunction of sister-chromatids occurs during the first cleavage division. This latter explanation has been urged by Ohno, Kaplan & Kinosita (1959), who found no evidence for non-disjunction of the X-and Y-chromosome in an extensive cytolosical examination of the mouse testis.

scholarly journals The potential for a released autosomal X-shredder becoming a driving-Y chromosome and invasively suppressing wild populations of malaria mosquitoes

2019 ◽  
Author(s):  
Yehonatan Alcalay ◽  
Silke Fuchs ◽  
Roberto Galizi ◽  
Federica Bernardini ◽  
Roya Elaine Haghighat-Khah ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Unexpected Event ◽  
Meiotic Sex Chromosome Inactivation ◽  
Ratio Distortion ◽  
High Fraction ◽  
Malaria Mosquitoes ◽  
Population Suppression

AbstractSynthetic sex-ratio distorters based on X-chromosome shredding are predicted to be more efficient than sterile males for population suppression of malaria mosquitoes using genetic control. X-chromosome shredding operates through the targeted elimination of X-chromosome-bearing gametes during male spermatogenesis, resulting in males that have a high fraction of male offspring. Strains harboring autosomal constructs containing a modified endonuclease I-PpoI have now been developed in the malaria mosquito Anopheles gambiae, resulting in strong sex-ratio distortion towards males. Data are being gathered for these strains for submission of regulatory dossiers for contained use and subsequent field release in West Africa. Since autosomal X-shredders are transmitted in a Mendelian fashion and can be selected against their frequency in the population is expected to decline once releases are halted. However, any unintended transfer of the X-shredder to the Y-chromosome could theoretically change these dynamics: This could lead to 100% transmission of the newly Y-linked X-shredder to the predominant male-biased offspring and its insulation from negative selection in females, resulting in its potential spread in the population and ultimately to suppression. Here, we analyze plausible mechanisms whereby an autosomal X-shredder could become linked to the Y-chromosome after release and provide data regarding its potential for activity should it become linked to the Y-chromosome. Our results strongly suggest that Y-chromosome linkage through remobilization of the transposon used for the initial genetic transformation is unlikely, and that, in the unexpected event that the X-shredder becomes linked to the Y-chromosome, expression and activity of the X-shredder would likely be inhibited by meiotic sex chromosome inactivation. We conclude that a functioning X-shredding-based Y-drive resulting from a naturally induced transposition or translocation of the transgene onto the Y-chromosome is unlikely.

Observations on the So-Called Sex Chromatin in Man

1957 ◽  
Vol 6 (3) ◽  
pp. 393-402 ◽  
Author(s):  
Juhan Reitalu
Keyword(s):  
Nuclear Structure ◽  
Y Chromosome ◽  
X Chromosome ◽  
Liver Tissue ◽  
Male And Female ◽  
Heterochromatic Segment ◽  
Sex Chromatin ◽  
The Difference ◽  
Diploid Cells

SUMMARYThe difference in nuclear structure between male and female tissues in man has been examined in liver tissue from three embryos of each sex. The so-called sex chromatin consists of a large heterochromatic segment of the X chromosome, thus existing in duplicate in female diploid cells. The two segments have a tendency of juxtaposition resulting in a larger heterochromatic body in female than in male cells. Beside the large heterochromatic segment the X chromosome has, in the tissues studied, a euchromatic segment attached through a small terminal heterochromatic knob to a nucleolus. In male cells the euchromatic segment of the X chromosome is often joined terminally to a small heterochromatic segment believed to belong to the Y chromosome.

scholarly journals Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression

2020 ◽  
Vol 12 (6) ◽  
pp. 965-977 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E Wright ◽  
Judith E Mank
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Rna Seq ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
Chromosome Integrity ◽  
Heterogametic Sex

Abstract The loss of recombination triggers divergence between the sex chromosomes and promotes degeneration of the sex-limited chromosome. Several livebearers within the genus Poecilia share a male-heterogametic sex chromosome system that is roughly 20 Myr old, with extreme variation in the degree of Y chromosome divergence. In Poecilia picta, the Y is highly degenerate and associated with complete X chromosome dosage compensation. In contrast, although recombination is restricted across almost the entire length of the sex chromosomes in Poecilia reticulata and Poecilia wingei, divergence between the X chromosome and the Y chromosome is very low. This clade therefore offers a unique opportunity to study the forces that accelerate or hinder sex chromosome divergence. We used RNA-seq data from multiple families of both P. reticulata and P. wingei, the species with low levels of sex chromosome divergence, to differentiate X and Y coding sequences based on sex-limited SNP inheritance. Phylogenetic tree analyses reveal that occasional recombination has persisted between the sex chromosomes for much of their length, as X- and Y-linked sequences cluster by species instead of by gametolog. This incomplete recombination suppression maintains the extensive homomorphy observed in these systems. In addition, we see differences between the previously identified strata in the phylogenetic clustering of X–Y orthologs, with those that cluster by chromosome located in the older stratum, the region previously associated with the sex-determining locus. However, recombination arrest appears to have expanded throughout the sex chromosomes more gradually instead of through a stepwise process associated with inversions.

Sex chromosome replication and sex chromatin inAkodon azarae (Rodentia Cricetidae)

1968 ◽  
Vol 38 (8) ◽  
pp. 343-347 ◽  
Author(s):  
N. O. Bianchi ◽  
F. N. Dulout ◽  
J. Contreras
Keyword(s):  
Sex Chromosome ◽  
Chromosome Replication ◽  
Sex Chromatin

TURNER'S SYNDROME WITH SECONDARY AMENORRHOEA AND SEX CHROMOSOME MOSAICISM

1964 ◽  
Vol 46 (3) ◽  
pp. 341-351 ◽  
Author(s):  
D. R. London ◽  
N. H. Kemp ◽  
R. Ellis ◽  
Ursula Mittwoch
Keyword(s):  
Bone Marrow ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Acrocentric Chromosome ◽  
Ring Chromosome ◽  
Cell Types ◽  
Abdominal Skin ◽  
Chromosome Mosaicism ◽  
Different Cell Types ◽  
Bone Marrow Blood

ABSTRACT A female patient is described aged 28 years, height 145 cm, with infantile genitalia, infantile uterus and atrophic ovaries and in whom menstruation had occurred over a period of five years. Chromosome studies from bone marrow, blood, skin (arm and abdominal wall) and both ovaries revealed sex chromosome mosaicism and a structurally abnormal X chromosome. Three cell lines were observed. The prevalent cell line which was present in cultures from all tissues had 45 chromosomes and an XO karyotype; cultures from all tissues except the abdominal skin contained cells with 46 chromosomes, with an X/deleted X karyotype (the latter in the form of a large acrocentric chromosome); lastly a small dot-like (ring?) chromosome was present as the 46th chromosome in some cells derived from the abdominal skin and right ovary. The frequency of the different cell types in cultures from the ovaries differed considerably from those of other tissues.

scholarly journals Dosage compensation and sex-chromatin in non-mammals

1964 ◽  
Vol 5 (3) ◽  
pp. 354-365 ◽  
Author(s):  
A. G. Cock
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Somatic Cells ◽  
Positive Evidence ◽  
Lymantria Monacha ◽  
Sex Chromatin ◽  
Heterogametic Sex

1. Inactivation of one X chromosome in somatic cells of female mammals is a form of dosage compensation of sex-linked genes, but the mechanism is entirely different from that operating in Drosophila. The latter is designated as dosage compensation sensu strictu.2. There is no dosage compensation of barred, sex-linked dilution or slow-feathering in domestic fowls, of almond or faded in pigeons, or of cinnamon in canaries. Among Lepidoptera the same is true of sex-linked melanism in Lymantria monacha and of a locus controlling haemolymph colour in Choritoneura spp. There is no positive evidence that dosage compensation occurs outside Drosophila and mammals.3. Sex-chromatin in female birds (heterogametic) has been reported by several authors; the genetical evidence is against the possibility that this represents (as in mammals) an inactivated X chromosome. Sex-chromatin in the heterogametic sex also occurs in some (not all) Lepidoptera and Heteroptera; in Heteroptera it usually represents a heteropyknotic Y chromosome.4. Some complications in Muller's theory of dosage compensation sensu strictu are discussed. Not all ‘compensatory modifiers’ are necessarily sex-linked.5. The problem of dosage compensation in species with impaternate males is discussed; fused in Habrobracon is not compensated.

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