Clues from other animals and theoretical considerations

Development ◽  
1987 ◽  
Vol 101 (Supplement) ◽  
pp. 3-4
Author(s):  
Anne McLaren
Keyword(s):  
Sex Determination ◽  
Genetic Control ◽  
Y Chromosome ◽  
X Chromosome ◽  
X Chromosomes ◽  
The Third ◽  
Mouse Species ◽  
Primary Male ◽  
Theoretical Considerations ◽  
State Of Activity

In the first two papers of this volume, the genetic control of sex determination in Caenorhabditis and Drosophila is reviewed by Hodgkin and by Nöthiger & Steinmarin-Zwicky, respectively. Sex determination in both cases depends on the ratio of X chromosomes to autosomes, which acts as a signal to a cascade of règulatory genes located either on autosomes or on the X chromosome. The state of activity of the last gene in the sequence determines phenotypic sex. In the third paper, Erickson & Tres describe the structure of the mouse Y chromosome and the polymorphisms that have been detected in different mouse species and strains. As in all mammals, the Y carries the primary male-determining locus; autosomal genes may also be involved in sex determination, but they must act down-stream from the Y-linked locus.

Determination of Sex Chromatin — A New Concept

1972 ◽  
Vol 21 (1-2) ◽  
pp. 149-170
Author(s):  
Syed Shane Raza Zaidi
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
X Chromosome ◽  
Mother Cell ◽  
Daughter Cell ◽  
Barr Body ◽  
X Chromosomes ◽  
Sex Chromatin

SummaryInstead of the random activation and/or inactivation of the X-chromosome in sex determination, as suggested by the Lyon's hypothesis, a proposal is made here that crossingover between the sister- and/or nonsisterstrands at the sticky or nonsticky loci, at heterochromatinizing regions and at the inactivating centers of the centromère, be responsible for the heterochromatinization and/or heteropyknotization of the X-chromosome. (This proposal will be called the Mustafa hypothesis.)Such would be the basis for the activation and/or inactivation of the X-chromatid(s), which would then replicate into a normal or a heterochromatic X-chromosome respectively. The heterochromatic X-chromosome may be transformed into a heteropyknotized mass of sex chromatin (Barr body). Translocation of the Y-chromosome and of some of the autosomes could also result in the same effect. Hence, the number of heterochromatinized X-chromosomes, and/or of heteropyknotized masses (Barr bodies), in each daughter-cell is directly proportional to half the number of chromatids involved in crossingover and/or translocation in the mother-cell.

Primary Genetic-Control of Sexual-Differentiation in Marsupials

1989 ◽  
Vol 37 (3) ◽  
pp. 443 ◽  
Author(s):  
G Shaw ◽  
MB Renfree ◽  
RV Short
Keyword(s):  
Genetic Control ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sexual Differentiation ◽  
Hormonal Control ◽  
Sexually Dimorphic ◽  
Processus Vaginalis ◽  
X Chromosomes

Marsupials, like eutherians, normally require the presence of a Y chromosome for testicular formation. However some sexually dimorphic characters such as the scrotum, mammary anlagen, gubernaculum and processus vaginalis appear to be under direct genetic rather than secondary hormonal control. Scrota1 development occurs where only a single X chromosome is functional, whilst two X chromosomes are necessary for pouch formation.

scholarly journals Inheritance of Chromosomes, Sex Determination, and the Human Genome

2018 ◽  
Vol 2 (1) ◽  
pp. 16-26 ◽  
Author(s):  
Nirmalchandra K. Shetty
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
X Chromosome ◽  
Cell Biology ◽  
Theoretical Research ◽  
Barr Body ◽  
X Chromosomes ◽  
New Model ◽  
Hypothesis Model ◽  
New Hypothesis

Who is the determining factor for the sex of the offspring—mother, father, or both parents? This fundamental hypothesis proposes a new model of sex determination, challenging the existing dogma that the male Y chromosome of the father is the sole determinant of the sex of the offspring. According to modern science, the 3 X chromosomes (male XY and female XX) are assumed to be similar, and the sex of the offspring is determined after the zygote is formed. In contrast to this, the new hypothesis based on theoretical research proposes that the 3 X chromosomes can be differentiated, based on the presence of Barr bodies. The first X in female XX chromosomes and X in male XY chromosomes are similar as they lack Barr body and are hereby denoted as ‘X’ and referred to as ancestral chromosomes. The second X chromosome in the female cells which is a Barr body, denoted as X, is different. This X chromosome along with the Y chromosome are referred to as parental chromosomes. Sperm with a Y chromosome can only fuse with an ovum containing the ‘X’ chromosome. Similarly, sperm with the ‘X’ chromosome can only fuse with an ovum containing the X chromosome. Cell biology models of gametogenesis and fertilization were simulated with the new hypothesis model and assessed. Only chromosomes that participated in recombination could unite to form the zygote. This resulted in a paradigm shift in our understanding of sex determination, as both parents were found to be equally responsible for determining the sex of the offspring. The gender of the offspring is determined during the prezygotic stage itself and is dependent on natural selection. A new dimension has been given to inheritance of chromosomes. This new model also presents a new nomenclature for pedigree charts. This work of serendipity may contribute to future research in cell biology, gender studies, genome analysis, and genetic disorders including cancer.

Major sex-determining genes and the control of sexual dimorphism in Caenorhabditis elegans

Genome ◽  
1989 ◽  
Vol 31 (2) ◽  
pp. 625-637 ◽  
Author(s):  
Jonathan Hodgkin ◽  
Andrew D. Chisholm ◽  
Michael M. Shen
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Germ Line ◽  
Cell Lineage ◽  
Regulatory Genes ◽  
Nematode Caenorhabditis Elegans ◽  
X Chromosomes ◽  
The Many ◽  
Lineage Analysis

Sex determination in Caenorhabditis elegans involves a cascade of major regulatory genes connecting the primary sex determining signal, X chromosome dosage, to key switch genes, which in turn direct development along either male or female pathways. Animals with one X chromosome (XO) are male, while animals with two X chromosomes (XX) are hermaphrodite: hermaphrodite development occurs because the action of the regulatory genes is modified in the germ line so that both sperm and oocytes are made inside a completely female soma. The regulatory genes are being examined by both genetic and molecular means. We discuss how these major genes, in particular the last switch gene in the cascade, tra-1, might regulate the many different sex-specific events that occur during the development of the hermaphrodite and of the male.Key words: nematode, Caenorhabditis elegans, sex determination, sexual differentiation, cell lineage analysis.

Roles of Anti-Müllerian hormone (Amh) and its duplicates in sex determination and germ cell proliferation of Nile tilapia

Genetics ◽  
2021 ◽  
Author(s):  
Xingyong Liu ◽  
Shengfei Dai ◽  
Jiahong Wu ◽  
Xueyan Wei ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Sex Determination ◽  
Germ Cell ◽  
Y Chromosome ◽  
X Chromosome ◽  
Nile Tilapia ◽  
Critical Period ◽  
Sex Reversal ◽  
Homozygous Mutation ◽  
Germ Cell Proliferation

Abstract Duplicates of amh are crucial for fish sex determination and differentiation. In Nile tilapia, unlike in other teleosts, amh is located on X chromosome. The Y chromosome amh (amh△-y) is mutated with 5 bp insertion and 233 bp deletion in the coding sequence, and tandem duplicate of amh on Y chromosome (amhy) has been identified as the sex determiner. However, the expression of amh, amh△-y and amhy, their roles in germ cell proliferation and the molecular mechanism of how amhy determines sex is still unclear. In this study, expression and functions of each duplicate were analyzed. Sex reversal occurred only when amhy was mutated as revealed by single, double and triple mutation of the three duplicates in XY fish. Homozygous mutation of amhy in YY fish also resulted in sex reversal. Earlier and higher expression of amhy/Amhy was observed in XY gonads compared with amh/Amh during sex determination. Amhy could inhibit the transcription of cyp19a1a through Amhr2/Smads signaling. Loss of cyp19a1a rescued the sex reversal phenotype in XY fish with amhy mutation. Interestingly, mutation of both amh and amhy in XY fish or homozygous mutation of amhy in YY fish resulted in infertile females with significantly increased germ cell proliferation. Taken together, these results indicated that up-regulation of amhy during the critical period of sex determination makes it the sex-determining gene, and it functions through repressing cyp19a1a expression via Amhr2/Smads signaling pathway. Amh retained its function in controlling germ cell proliferation as reported in other teleosts, while amh△-y was nonfunctionalized.

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.

CYTOTAXONOMY AND SEX DETERMINATION OF RUMEX PAUCIFOLIUS

1956 ◽  
Vol 34 (2) ◽  
pp. 261-268 ◽  
Author(s):  
Áskell Löve ◽  
Nina Sarkar
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
The Other ◽  
Large Chromosome ◽  
Dioecious Species ◽  
The Third ◽  
Male Sex ◽  
Morphological Differences

The western North American dioecious species Rumex paucifolius is shown to be a tetraploid with 2n = 28 chromosomes. It is the third tetraploid known within the subgenus Acetosa, and the first polyploid dioecious taxon of that group, the others having either 2n = 14 ♂, 15 ♀ (R. Acetosa and relatives), or 2n = 8 ♂, 9 ♀ (R. hastatulus). The sex chromosomes of R. paucifolius are of the XX:XY type, the male sex being heterogametic. The X is a large chromosome, while the Y is the smallest chromosome of the complement. The mechanism of sex determination of R. paucifolius follows the Melandrium–Acetosella scheme with strongly epistatic male determinants in the Y–chromosome. Other dioecious Acetosae follow the Drosophila–Acetosa scheme of sex determination with a balance between the number of X and autosome complements, the Y being sexually inert. It is concluded from the observed cytogenetical and morphological differences that R. paucifolius should constitute a section of its own, Paucifoliae, which should be placed as far as possible from the section Acetosa, though within the same subgenus. The other American dioecious endemic, R. hastatulus, is placed in a subsection of the section Acetosa.

scholarly journals AL-QUR'AN DAN MATERIAL GENETIK DALAM SEL KELAMIN PRIA PENENTU JENIS KELAMIN BAYI

2018 ◽  
Vol 8 (2) ◽  
pp. 141-162
Author(s):  
Bayyinatul Muchtaromah
Keyword(s):  
Molecular Biology ◽  
Sex Determination ◽  
Y Chromosome ◽  
X Chromosome ◽  
Seventh Century ◽  
The Other ◽  
Male And Female

In many verses of al-Qur'an, men are called to pay their attention to understand how they were created. Human creation and incredible aspects followed were strongly mentioned in many verses in detail until it's impossible for anyone who lived in the seventh century to recognize it. One of them was the information saying that the determinant of baby gender is the spermatozoa coming from men sperm. Allah said in his verse: "and that He (Allah) creates in pairs, male and female. From Nutfah (drops of semen male and female discharge) when it is emitted" (translation of al-Qur'an 53 verse 45-46). Branches of knowledge which have developed, such as Genetics and Molecular Biology, have proved scientifically the information accuracy which has been given by al-Qur'an. Nowadays it has been well-known that sex determination is determined by sperm of man and in fact women play no roles in this determination. If the ovum fuses with sperm which carries Y chromosome than the baby will be born as a male. Conversely, if the sperm carries X chromosome than the baby will be a female. In the other word, the sex of the baby is determined by the kind of man's sperm chromosome which fuses with women's ovum.

Identification of X chromosome regions in Caenorhabditis elegans that contain sex-determination signal elements.

Genetics ◽  
1994 ◽  
Vol 138 (4) ◽  
pp. 1105-1125
Author(s):  
C C Akerib ◽  
B J Meyer
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Dosage Compensation ◽  
X Chromosomes ◽  
Sensitive Region ◽  
Signal Element ◽  
Number Of Genes ◽  
Mutant Phenotypes ◽  
Chromosome Regions

Abstract The primary sex-determination signal of Caenorhabditis elegans is the ratio of X chromosomes to sets of autosomes (X/A ratio). This signal coordinately controls both sex determination and X chromosome dosage compensation. To delineate regions of X that contain counted signal elements, we examined the effect on the X/A ratio of changing the dose of specific regions of X, using duplications in XO animals and deficiencies in XX animals. Based on the mutant phenotypes of genes that are controlled by the signal, we expected that increases (in males) or decreases (in hermaphrodites) in the dose of X chromosome elements could cause sex-specific lethality. We isolated duplications and deficiencies of specific X chromosome regions, using strategies that would permit their recovery regardless of whether they affect the signal. We identified a dose-sensitive region at the left end of X that contains X chromosome signal elements. XX hermaphrodites with only one dose of this region have sex determination and dosage compensation defects, and XO males with two doses are more severely affected and die. The hermaphrodite defects are suppressed by a downstream mutation that forces all animals into the XX mode of sex determination and dosage compensation. The male lethality is suppressed by mutations that force all animals into the XO mode of both processes. We were able to subdivide this region into three smaller regions, each of which contains at least one signal element. We propose that the X chromosome component of the sex-determination signal is the dose of a relatively small number of genes.

Mapping the Y chromosome

Development ◽  
1987 ◽  
Vol 101 (Supplement) ◽  
pp. 39-39
Author(s):  
P. N. Goodfellow
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
X Chromosome ◽  
Dna Probes ◽  
Genetic Maps ◽  
Variable Amount ◽  
Regional Localization ◽  
Y Chromosomes ◽  
Xx Males ◽  
Human Y Chromosome

DNA probes isolated from the human Y chromosome have been used to resolve two fundamental problems concerning the biology of sex determination in man. Coincidentally, resolution of these problems has generated genetic maps of the short arm of the human Y chromosome and has allowed the regional localization of TDF. The first problem to be solved was the origin of XX males (de la Chapelle, this symposium): the majority of XX males are caused by a telomeric exchange between the X and Y chromosomes that results in TDF and a variable amount of Y-derived material being transferred to the X chromosome. The differing amounts of Y-derived material present in XX males has been used as the basis of a ‘deletion’ map of the Y chromosome (Müller; Ferguson-Smith & Affara; this symposium).

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