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The contrasting role of heterochromatin in the differentiation of sex chromosomes: an overview from Neotropical fishes

Cioffi, M. B.; Moreira-Filho, O.; Toledo, Lurdes Foresti de Almeida; Bertollo, L. A. C.
Fonte: WILEY-BLACKWELL; MALDEN Publicador: WILEY-BLACKWELL; MALDEN
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.45%
During the evolutionary process of the sex chromosomes, a general principle that arises is that cessation or a partial restriction of recombination between the sex chromosome pair is necessary. Data from phylogenetically distinct organisms reveal that this phenomenon is frequently associated with the accumulation of heterochromatin in the sex chromosomes. Fish species emerge as excellent models to study this phenomenon because they have much younger sex chromosomes compared to higher vertebrates and many other organisms making it possible to follow their steps of differentiation. In several Neotropical fish species, the heterochromatinization, accompanied by amplification of tandem repeats, represents an important step in the morphological differentiation of simple sex chromosome systems, especially in the ZZ/ZW sex systems. In contrast, multiple sex chromosome systems have no additional increase of heterochromatin in the chromosomes. Thus, the initial stage of differentiation of the multiple sex chromosome systems seems to be associated with proper chromosomal rearrangements, whereas the simple sex chromosome systems have an accumulation of heterochromatin. In this review, attention has been drawn to this contrasting role of heterochromatin in the differentiation of simple and multiple sex chromosomes of Neotropical fishes...

No evidence of predation causing female-biased sex ratios in marine pelagic copepods

Gusmão, Luiz Felipe Mendes de; McKinnon, A. David; Richardson, Anthony J.
Fonte: Oldendorf Publicador: Oldendorf
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.5%
Although sex ratios close to unity are expected in dioecious species, biased sex ratios are common in nature. It is essential to understand causes of skewed sex ratios in situ, as they can lead to mate limitation and have implications for the success of natural populations. Female-skewed sex ratios are commonly observed in copepods in situ. Here we discuss the challenges of copepod sex ratio research and provide a critical review of factors determining copepod sex ratios, focusing on 2 main objectives. The first is a critique of the male predation theory, which is currently the main process thought to be responsible for female-skewed sex ratios. It assumes that males have higher mortality because of increased vulnerability to predation during their search for mates. We show that there is little support for the male predation theory, that sex ratios skewed toward females occur in the absence of predation, that sex ratios are not related to predation pressure, and that where sex-skewed predation does occur, it is biased toward females. Our second objective is to suggest alternative hypotheses regarding the determination of sex ratios. We demonstrate that environmental factors, environmental sex determination and sex change have strong effects on copepod sex ratios...

Sex determination studies in two species of teleost fish, Oreochromis niloticus and Leporinus elongatus

Baroiller, Jean-Francois; Nakayama, Ichiro; Foresti, Fausto; Chourrout, Daniel
Fonte: Acad Sinica Inst Zoology Publicador: Acad Sinica Inst Zoology
Tipo: Artigo de Revista Científica Formato: 279-285
ENG
Relevância na Pesquisa
36.48%
Genetic analyses of sex determination have identified sex chromosomes in many teleost fish species. However, there are several cases for which sex ratios do not fit perfectly with the expectations of heterogametic systems, suggesting the influence of either minor sex determining genes or environmental influences on the process of sex differentiation. The frequent absence of sex chromosome markers makes the identification of minor sex-determining genes very difficult. It is easier to test first the hypothesis of environmental sex determination (ESD) by studying the temperature effect, since temperature-dependent sex determination has been demonstrated to occur in several vertebrate groups including 1 fish species. To contribute to a better understanding of fish sex determination, we have tested the effects of high temperatures on sex ratios of Oreochromis niloticus, and have attempted to isolate sex chromosome molecular markers in Leporinus elongatus. Treatments of O. niloticus fry at 36 degrees C applied for 10 days and more, and starting 1 week after fertilization markedly increased the proportion of males, and progeny-testing these males confirmed that some of them are sex-reversed genetic females. Two non-coding sequences of L. elongatus Z and W chromosomes were cloned by genomic subtraction. They cross-hybridized with the genome of a close species without providing sex-specific patterns. A collection of L. elongates individuals was subjected to gonadal and chromosomal sexing...

Variability in Sex-Determining Mechanisms Influences Genome Complexity in Reptilia

Janes, D.E.; Organ, C.L.; Edwards, S.V.
Fonte: S. Karger AG Publicador: S. Karger AG
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
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In this review, we describe the history of amniote sex determination as a classic example of Darwinian evolution. We suggest that evolutionary changes in sex determination provide a foundation for understanding important aspects of chromosome and genome organization that otherwise appear haphazard in their origins and contents. Species with genotypic sex determination often possess heteromorphic sex chromosomes, whereas species with environmental sex determination lack them. Through a series of mutations followed by selection at key genes, sex-determining mechanisms have turned over many times throughout the amniote lineage. As a consequence, amniote genomes have undergone gains or losses of sex chromosomes. We review the genomic and ecological contexts in which either temperature-dependent or genotypic sex determination has evolved. Once genotypic sex determination emerges in a lineage, viviparity and heteromorphic sex chromosomes become more likely to evolve. For example, in extinct marine reptiles, genotypic sex determination apparently led to viviparity, which in turn facilitated their pelagic radiation. Sex chromosomes comprise genome regions that differ from autosomes in recombination rate, mutation rate, levels of polymorphism...

Sequence and gene content of a large fragment of a lizard sex chromosome and evaluation of candidate sex differentiating gene R-spondin 1

Ezaz, Tariq; Azad, Bhumika; O’Meally, Denis; Young, Matthew J; Matsubara, Kazumi; Edwards, Melanie J; Zhang, Xiuwen; Holleley, Clare E; Deakin, Janine E; Marshall Graves, Jennifer A; Georges, Arthur; Edwards, Scott V; Sarre, Stephen D
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.47%
Background: Scant genomic information from non-avian reptile sex chromosomes is available, and for only a few lizards, several snakes and one turtle species, and it represents only a small fraction of the total sex chromosome sequences in these species. Results: We report a 352 kb of contiguous sequence from the sex chromosome of a squamate reptile, Pogona vitticeps, with a ZZ/ZW sex microchromosome system. This contig contains five protein coding genes (oprd1, rcc1, znf91, znf131, znf180), and major families of repetitive sequences with a high number of copies of LTR and non-LTR retrotransposons, including the CR1 and Bov-B LINEs. The two genes, oprd1 and rcc1 are part of a homologous syntenic block, which is conserved among amniotes. While oprd1 and rcc1 have no known function in sex determination or differentiation in amniotes, this homologous syntenic block in mammals and chicken also contains R-spondin 1 (rspo1), the ovarian differentiating gene in mammals. In order to explore the probability that rspo1 is sex determining in dragon lizards, genomic BAC and cDNA clones were mapped using fluorescence in situ hybridisation. Their location on an autosomal microchromosome pair, not on the ZW sex microchromosomes, eliminates rspo1 as a candidate sex determining gene in P. vitticeps. Conclusion: Our study has characterized the largest contiguous stretch of physically mapped sex chromosome sequence (352 kb) from a ZZ/ZW lizard species. Although this region represents only a small fraction of the sex chromosomes of P. vitticeps...

Transactional Sex as a Response to Risk in Western Kenya

Robinson, Jonathan; Yeh, Ethan
Fonte: Banco Mundial Publicador: Banco Mundial
Relevância na Pesquisa
36.52%
Formal and informal commercial sex work is a way of life for many poor women in developing countries. Though sex workers have long been identified as crucial in affecting the spread of HIV/AIDS, particularly in Sub-Saharan Africa, the nature of sex-for-money transactions remains poorly understood. Using a unique panel dataset constructed from 192 self-reported sex worker diaries which include detailed information on sexual behavior, labor supply, and health shocks, the authors find that sex workers adjust their supply of risky, better compensated sex to cope with unexpected health shocks, exposing themselves to increased risk of HIV infection. In particular, women are 3.1 percent more likely to see a client, 21.2 percent more likely to have anal sex, and 19.1 percent more likely to have unprotected sex on days in which a household member falls ill. Women also increase their supply of risky sex on days after missing work due to symptoms from a sexually transmitted infection. Given that HIV prevalence has been estimated at 9.8 percent in this part of Kenya...

Sex Workers and the Cost of Safe Sex : The Compensating Differential for Condom Use in Calcutta

Rao, Vijayendra; Gupta, Indrani; Jana, Smarajit
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
EN_US
Relevância na Pesquisa
36.51%
The practice of safe sex by commercial sex workers is considered central to preventing the transmission of AIDS in developing countries. The authors estimate the compensating differential for condom use among sex workers in Calcutta, based on results from a survey conducted in 1993. If, as suggested by anecdotal evidence, this loss in income is large, it would indicate the existence of strong disincentives for practicing safe sex. To identify the relationship between condom use and the average price per sex act, they follow an instrumental variable approach, exploiting an intervention program focused on providing information about the AIDS virus and about safe sex practices. The program, instituted in 1992, was not systematically administered. Using this method, they found that sex workers who always use condoms face a loss of 79 percent in the average earnings per sex act.

Avaliação da qualidade de vida de pacientes adultos com distúrbio do desenvolvimento sexual (DDS) 46,XX e 46,XY em uma larga coorte de um único centro terciário; Quality of life in a large cohort of adult Brazilian patients with 46,XX and 46,XY disorders of sex development (DSD) from a single tertiary centre

Amaral, Rita de Cássia do
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/07/2015 PT
Relevância na Pesquisa
36.48%
Introdução: As doenças crônicas que envolvem tratamento clínico e cirúrgico podem comprometer a qualidade de vida. Poucos estudos analisam a qualidade de vida de pacientes com distúrbios do desenvolvimento sexual (DDS). O objetivo foi avaliar a qualidade de vida de pacientes com DDS com o diagnostico etiológico estabelecido, seguidos até a idade adulta em um único centro terciário. Pacientes e Métodos: 144 pacientes adultos com DDS (56 pacientes com DDS 46,XX - 49 com sexo social feminino e 7 com o sexo social masculino, bem como, 88 pacientes com DDS 46,XY - 54 com sexo social feminino e 34 com sexo social masculino). Instrumento: A avaliação da qualidade de vida foi realizada através do questionário WHOQOL-Bref. Resultados: Os pacientes com DDS 46,XX e 46,XY apresentaram escores de qualidade de vida semelhante e comparáveis aos escores da população brasileira geral. Os pacientes com DDS do sexo social masculino tiveram melhores escores no domínio psicológico do que os pacientes do sexo social feminino, da mesma forma que a população geral brasileira. Dentro do grupo DDS 46,XY, também os pacientes com o sexo social masculino tiveram melhores escores de qualidade de vida em comparação aos do sexo social feminino. Para avaliar o impacto na qualidade de vida dos pacientes com DDS 46...

Transcriptome Assembly and Molecular Evolutionary Analysis of Sex-Biased Genes in the Guppy (Poecilia reticulata)

Sharma, Eshita
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
EN
Relevância na Pesquisa
36.51%
It is a phenomenon universally seen that males and females of a species show phenotypic differences as they evolve under often diverging sex-specific selection pressures. The evolution and maintenance of their sexual dimorphism is generally associated with gene expression divergence between the sexes. Genes that show enriched expression in one sex, also called sex-biased genes, often show rapid molecular evolution. Furthermore, sex-biased genes have also been found to be over-represented on X or Z chromosomes in several species with differentiated sex chromosomes or neo-sex chromosomes. While research on sex-biased genes in drosophilids, mammals and birds has developed in the last decade, there is relatively little known about sex-biased genes in teleost species with largely undifferentiated sex-chromosomes of recent origin. A case in point is that of the Trinidadian guppy, Poecilia reticulata, which is the focal species of my thesis. In this dissertation, I investigate sex-biased gene expression in guppy, a fresh-water fish with XY sex-determination and Y-linked inheritance of male-advantageous traits. Guppies display sexual dimorphism in size, ornaments, and behavior, traits that are shaped by both natural and sexual selection in the wild. My first task was to assemble a transcriptome reference using deep sequencing of cDNA. I compared several methods of assembly with RNA sequencing (RNA-seq) data and assembled and annotated a reference transcriptome combining a genome-independent and a genome-guided assembly. Subsequently...

The Global HIV Epidemics among Sex Workers

Kerrigan, Deanna; Wirtz, Andrea; Baral, Stefan; Decker, Michele; Murray, Laura; Poteat, Tonia; Pretorius, Carel; Sherman, Susan; Sweat, Mike; Semini, Iris; N'Jie, N'Della; Stanciole, Anderson; Butler, Jenny; Osornprasop, Sutayut; Oelrichs, Robert; Beyrer,
Fonte: Banco Mundial Publicador: Banco Mundial
Tipo: Publications & Research :: Publication; Publications & Research :: Publication
ENGLISH
Relevância na Pesquisa
36.51%
Since the beginning of the epidemic sex workers have experienced a heightened burden of HIV across settings, despite their higher levels of HIV protective behaviors (UNAIDS, 2009). Unfairly, sex workers have often been framed as 'vectors of disease' and 'core transmitters' rather than workers and human beings with rights in terms of HIV prevention and beyond. By gaining a deeper understanding of the epidemiologic and broader policy and social context within which sex work is set one begins to quickly gain a sense of the complex backdrop for increased risk to HIV among sex workers. This backdrop includes the critical role of stigma, discrimination and violence faced by sex workers, as well as, the importance of community empowerment and mobilization among sex workers to address these regressive forces. The eight country case studies work to highlight the experiences of diverse populations of and contexts for sex work across settings. Given the limited epidemiologic and intervention evaluation data available among male and transgender sex workers...

Sex-Selective Abortions, Fertility, and Birth Spacing

Portner, Claus C.
Fonte: World Bank Group, Washington, DC Publicador: World Bank Group, Washington, DC
Tipo: Publications & Research; Publications & Research :: Policy Research Working Paper
ENGLISH; EN_US
Relevância na Pesquisa
36.48%
Previous research on sex-selective abortions has ignored the interactions between fertility, birth spacing, and sex selection, despite both fertility and birth spacing being important considerations for parents when deciding on the use of sex selection. This paper presents a novel approach that jointly estimates the determinants of sex-selective abortions, fertility, and birth spacing, using data on Hindu women from India's National Family and Health Surveys. Women with eight or more years of education in urban and rural areas are the main users of sex-selective abortions and they also have the lowest fertility. Predicted lifetime fertility for these women declined 11 percent between the 1985-1994 and 1995-2006 periods, which correspond to the periods of time before and after sex selection became illegal. Fertility is now around replacement level. This decrease in fertility has been accompanied by a 6 percent increase in the predicted number of abortions during the childbearing years between the two periods...

Perfil morfo-funcional da inversão de sexo em Synbranchidae (Teleostei: Synbranchiformes); Morpho-functional characteristics of sex reversal in Synbranchidae (Teleostei: Synbranchiformes)

Fernanda Natalia Antoneli
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/08/2006 PT
Relevância na Pesquisa
36.49%
Os peixes teleósteos exibem vários padrões sexuais durante sua ontogenia, nos quais as gõnadas se transformam em ovários ou testículos funcionais. Nas distintas Ordens podem ser encontradas espécies gonocóricas, assim como hermafroditas, tanto simultâneas quanto seqüenciais ou consecutivas. No hermafroditismo seqüencial (protândrico ou protogínico), a mudança de sexo nos indivíduos adultos envolve a degeneração do tecido gonadal do primeiro sexo e o crescimento e maturação do tecido do sexo oposto, passando por uma fase de intersexo. Nas espécies hermafroditas protogínicas, mais frequentemente observada nos teleósteos, os individuos desenvolvem-se como fêmeas e, posteriormente, na vida adulta, seus ovários funcionais são substituídos por testículos, transformando-as em machos reprodutivamente ativos. Fatores internos e externos (ambientais) parecem controlar a mudança de sexo nas espécies hermafroditas seqüenciais. Nos vertebrados, o funcionamento do sistema reprodutor envolve o sistema nervoso e complexas vias de feedback hormonais, ambos integrados no chamado eixo hipotalâmico-hipofisário-gonadal. Nos peixes teleósteos, os esteróides sexuais, assim como os hormônios hipotalâmicos e adenohipofisários são considerados os principais fatores que controlam o desenvolvimento sexual gonadal...

Endocrine sex control strategies for the feminization of teleost fish

Piferrer, Francesc
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 918459 bytes; application/pdf
ENG
Relevância na Pesquisa
36.46%
53 pages, 11 figures, 3 tables.-- Printed version published Jun 2001.; In many species of cultured finfish, females exhibit higher growth rates than males and attain larger sizes. In addition, in some species, males mature before reaching marketable size. Together, this results in a larger dispersion of sizes and an overall reduction in production. Therefore, there is great interest from the private sector to produce all-female stocks. This review concentrates on the use of oestrogens for sex control, discussing the advantages of producing monosex female stocks for finfish aquaculture, and pointing out those cases in which hormonal sex reversal technology is worth applying. The biological basis on which hormonal sex manipulation rests, the process of sex differentiation—which, compared to that of other vertebrates, is quite labile in teleost fish—is described in order to understand the effects of treatments. Sex control is typically achieved by exposing sexually undifferentiated fish to exogenous steroids in order to direct the process of sex differentiation towards the desired sex. These treatments finish months or years before marketing and steroid residues disappear in less than a month after the end of treatment. The currently available methods to produce monosex female stocks...

Temperature-Dependent Sex Determination in Fish Revisited: Prevalence, a Single Sex Ratio Response Pattern, and Possible Effects of Climate Change

Ospina-Álvarez, Natalia; Piferrer, Francesc
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artículo Formato: 470051 bytes; application/pdf
ENG
Relevância na Pesquisa
36.47%
11 pages, 5 figures, 2 tables.-- PMID: 18665231 [PubMed].-- Supporting information available: Supplementary Table "Field and laboratory data used for the assessment of the presence of temperature-dependent sex determination in gonochoristic fish" and list of references.; [Background] In gonochoristic vertebrates, sex determination mechanisms can be classified as genotypic (GSD) or temperature-dependent (TSD). Some cases of TSD in fish have been questioned, but the prevalent view is that TSD is very common in this group of animals, with three different response patterns to temperature.; [Methodology/Principal Findings] We analyzed field and laboratory data for the 59 fish species where TSD has been explicitly or implicitly claimed so far. For each species, we compiled data on the presence or absence of sex chromosomes and determined if the sex ratio response was obtained within temperatures that the species experiences in the wild. If so, we studied whether this response was statistically significant. We found evidence that many cases of observed sex ratio shifts in response to temperature reveal thermal alterations of an otherwise predominately GSD mechanism rather than the presence of TSD. We also show that in those fish species that actually have TSD...

Determining the size of the male-specific region in the genome of the scuttle fly, Megaselia scalaris, a potential model system for the earliest stages of sex chromosome evolution

Peneva, Ralitza H.
Fonte: Universidade Duke Publicador: Universidade Duke
Publicado em 06/09/2012 EN_US
Relevância na Pesquisa
36.47%
Modern day whole-genome sequencing and the ability to make comparisons across many taxa have significantly advanced the study of sex chromosome evolution. The scuttle fly, Megaselia scalaris, is an appropriate model system for studying sex chromosome evolution exhibits sex chromosomes that are homomorphic in size, containing differences that are difficult to detect even microscopically. Presumably, sex in M. scalaris is determined by the presence or absence of a male-determining region, or sex realizer (M), that transposes among chromosomes at a low rate, essentially creating novel Y-chromosomes out of autosomes. M. scalaris would thus serve as a good model for exploring the primary stages of sex chromosome evolution. However, to serve as such a model, the identity and size of the male-specific region must be identified as a boundary within which to search for the sex realizer. This study focused on elucidating the relative size of the male-specific region in M. scalaris in relation to the genome. I compared previously generated genome sequences from male and female M. scalaris to isolate suggested regions unique to the male sex. Through a systematic approach involving sequencing, primer design, and PCR, I found the M. scalaris genome to be 27% male-specific...

Descriptors and Correlates of Sex Trading Amongst Active Methamphetamine Users in Cape Town, South Africa

Lion, Ryan Ridenour
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2015
Relevância na Pesquisa
36.48%

Introduction: South Africa has witnessed a tremendous rise in methamphetamine consumption since the year 2000. Sex trading is a phenomenon that has been observed in active drug users, globally and within South Africa, and has been associated with risks for HIV infection and violence. This paper is a secondary analysis examining sex trading among active methamphetamine users in Cape Town, South Africa. Methods: Respondent driven sampling was used to recruit 360 active methamphetamine users in a peri-urban township in Cape Town. A structured clinical interview and computerized survey were used to assess history of sex trading, demographics, drug use, sexual risk behaviors, history of violence, and mental health. Logistic regression models were used to examine predictors of sex trading, separately for men and women. Results: In a total sample of 201 men and 159 women, 40% of men and 33% of women endorsed trading sex for tik or money in the past 3 months. Those who traded sex were more likely to meet the criteria for ICD-10 amphetamine dependence among both men (OR=4.59, 95% CI=1.31-16.13) and women (OR=8.00, 95% CI: 1.02-62.59). Men who were concurrent heroin users were also more likely to exchange sex (OR=2.58, 95% CI: 1.06-6.28). Sexual risk behaviors were significantly associated with sex trading. Notably...

A systems-level view of mammalian sex determination.

Munger, Steven Carmen
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2010
Relevância na Pesquisa
36.47%

Pathologies of sexual development are common in humans and reflect the precarious processes of sex determination and sexual differentiation. The gonad forms as a bipotential organ, and recent results from the Capel lab revealed that it is initially balanced between testis and ovarian fates by opposing and antagonistic signaling networks. In XY embryos, this balance is disrupted by the transient expression of the Y-linked gene, Sry, which activates genes that promote the testis pathway and oppose the ovarian pathway. While the roles of a few genes have been defined by mutation, current evidence suggests that the interactions of many genes and signaling pathways are involved in the establishment of sexual fate. For example, most cases of disorders of sexual development (DSDs) are unexplained by mutations in known sex determination genes. In addition, recent microarray studies in the mouse revealed that nearly half the transcriptome is expressed in the gonad at the time of sex determination (Embryonic day 11.5, or E11.5), and as many as 1,500 genes are expressed in a sexually dimorphic pattern at this early stage. Thus the sexual fate decision in the developing gonad likely depends on a complex network of interacting factors that converge on a critical threshold.

To begin to elucidate the transcription network topology underlying sex determination...

Unintended pregnancy among female sex workers in Mekelle city, northern Ethiopia: a cross-sectional study

Weldegebreal, R.; Melaku, Y.A.; Alemayehu, M.; Gebrehiwot, T.G.
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
36.46%
BACKGROUND: Unintended pregnancy is a significant public health concern in the world. Particularly, female sex workers are exposed to the risk of unintended pregnancy, abortion and their consequences. The aim of this study was, therefore, to assess unintended pregnancy and associated factors among female sex workers in Mekelle city, northern Ethiopia. METHODS: A community based cross-sectional study was conducted among 346 female sex workers from five Kebelles (smallest administrative units in Ethiopia) of Mekelle city from March-April, 2014. Sex workers were selected with simple random sampling technique using sampling frame obtained from urban health extension program. Epi-data version 3.1 was used to enter data and analysis was done using SPSS version 20. Bivariate and multivariate logistic regressions were performed to identify factors associated with unintended pregnancy using odds ratio and 95% confidence interval with P-value of 0.05. RESULTS: The magnitude of unintended pregnancy among female sex workers in the past two years was 28.6%. During this period, 59 women had abortion which represents three-fifths, (59.6%), of those who had unintended pregnancies, and 17.1% of all female sex workers. Female sex workers who gave birth and had history of abortion formerly had 3.1 (AOR = 3.07...

Evolution of mammalian sex chromosomes and sex determination genes: insights from monotremes.

Toledo-Flores, Deborah Fernanda
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2015
Relevância na Pesquisa
36.5%
Genetic sex determination systems are generally based on the presence of differentiated sex chromosomes. Birds have a ZZ/ZW sex chromosome system in which males are ZZ and females ZW, whereas mammals have an XX/XY system with males being XY and females XX. Monotremes have an extraordinary sex chromosome system that consists of multiple sex chromosomes: 5X5Y in platypus and 5X4Y in echidna. Intriguingly, the monotreme sex chromosomes show extensive homology to the bird ZW and not to the therian XY. However, sex determination in monotremes is still a mystery; the Y-specific Sry gene that triggers male sex determination in therian mammals is absent and so far very few genes have been identified on Y chromosomes in monotremes. To gain more insights into the gene content of Y-chromosomes and to identify potential sex determination genes in the platypus a collaborative large scale transcriptomic approach led to the identification of new male specific genes including the anti-Muellerian hormone AMH that I mapped to Y₅, this makes Amhy an exciting new candidate for sex determination in monotremes. Platypus chromosome 6 is largely homologous to the therian X and therefore it represents the therian proto sex chromosome. In addition, this autosome features a large heteromorphic nucleolus organizer region (NOR) and associates with the sex chromosomes during male meiosis (Casey and Daish personal communication). I investigated chromosome 6 heteromorphism in both sexes and found a number of sex-specific characteristics related to the extent of the NOR heteromorphism...

Percepções de professores portugueses sobre educação sexual; Percepciones de profesores portugueses sobre educación sexual; Perceptions of Portuguese teachers about sex education

Ramiro, Lúcia; Matos, Margarida Gaspar de
Fonte: Universidade de São Paulo. Faculdade de Saúde Pública Publicador: Universidade de São Paulo. Faculdade de Saúde Pública
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf; application/pdf
Publicado em 01/08/2008 POR; ENG
Relevância na Pesquisa
36.46%
OBJETIVO: Avaliar percepções e atitudes em relação à educação sexual entre professores portugueses do ensino básico e secundário. MÉTODOS: Participaram do estudo 371 professores de ambos os sexos, do segundo e terceiro ciclos e do ensino secundário do continente Português, entre Fevereiro e Março de 2006. A coleta de dados foi feita por meio de questionário, pela técnica bola de neve, constituído por duas partes; a primeira abordava dados sociodemográficos, caracterização profissional, crenças religiosas, formação e experiência em educação sexual em meio escolar. A segunda parte foi composta por escalas relativas a atitudes, importância atribuída a temas de educação sexual e nível de ensino para introduzir tópicos de educação sexual. A análise das diferenças entre géneros, entre professores com e sem experiência em educação sexual, e entre professores com e sem formação complementar na área foi efectuada pela análise de variância ANOVA. RESULTADOS: Os professores, no geral, revelaram quer atitude quer importância médias/altas em relação à educação sexual. Imagem corporal foi o único tópico que deveria ser introduzido no primeiro ciclo. As professoras [F(1;366)=7,772; p=0,006] por oposição aos professores...