Every Cell Has a Sex: X and Y and the Future of Health Care

Step 2 of 2

5 or more characters. Case sensitive.
At least 10 characters long. No personal contact info.
Need help? Try these tools:
×

Error! We can’t register you at this time.

By registering on 98club.info, I certify I am at least 18 years old and have read and agree to its Terms of Use and Privacy Policy, and consent to the use of Cookies.
By registering on 98club.info, we certify we are at least 18 years old and have read and agree to its Terms of Use and Privacy Policy, and consent to the use of Cookies.
By registering on 98club.info, I/we certify I am/we are at least 18 years old and have read and agree to its Terms of Use and Privacy Policy, and consent to the use of Cookies.
    AVN award badges
    Going Beyond the Gonads See Details



    Navigation menu
    98club.info

    The XY sex-determination system is the sex-determination system found in humansmost other mammalssome insects Drosophilasome snakes, and some plants Ginkgo. In this system, the sex of an individual is determined by a pair of sex chromosomes. Females typically have two of the same kind of sex chromosome XXand are called the homogametic sex.

    Males typically have two different kinds of sex chromosomes XYand are called the heterogametic sex. In humans, the секс of the Y chromosome is responsible for triggering male development; in the absence of the Y chromosome, the fetus will undergo female development. More specifically, it is the SRY gene located on the Y chromosome that is of importance to male differentiation.

    Variations to the sex gene karyotype could include rare disorders such as XX males often due to translocation of the SRY gene to the X chromosome or XY gonadal dysgenesis in people who are externally female due to mutations in the SRY gene. The XY system contrasts in several ways with the ZW sex-determination system found in birdssome insects, many reptilesand various other animals, секс which the heterogametic sex is female. It had been thought for several decades that in all snakes sex was determined by the ZW system, but there had been observations of unexpected effects in секс genetics of species in the families Boidae and Pythonidae ; for example, parthenogenic reproduction produced only females rather than секс, which is the opposite of what is to be expected in the ZW system.

    In the early years of the 21st century such observations prompted research that demonstrated that all pythons and boas so far investigated definitely have the XY system of sex determination.

    A temperature-dependent sex determination system is found in some reptiles. All animals have a set of DNA coding for genes present on chromosomes. In humans, most mammals, and some other species, two of the chromosomescalled the X chromosome and Y chromosomecode for sex.

    In these species, one or more genes are present on their Y chromosome that determine maleness. In this process, an X chromosome and a Y chromosome act to determine the sex of offspring, often due to genes located on the Y chromosome that code for maleness.

    Offspring have two sex chromosomes: an offspring with two X chromosomes will develop female characteristics, and an offspring with an X and a Y chromosome will develop male characteristics. In humans, half of spermatozoons carry X chromosome and the other half Y chromosome. Presence of this gene starts off the process of virilization. This and other factors result in the sex differences in humans. The inactivated X chromosome remains within a cell as a Barr body.

    Humans, as well as some other organisms, can have a rare chromosomal arrangement that is contrary to their phenotypic sex; for example, XX males or XY gonadal dysgenesis see androgen insensitivity syndrome. Additionally, an abnormal number of sex chromosomes aneuploidy may be present, such as Turner's syndromein which a single X chromosome is present, and Klinefelter's syndromein which two X chromosomes and a Y chromosome are present, XYY syndrome and XXYY syndrome.

    In most mammals, sex is determined by presence of the Y chromosome. SRY is a sex-determining gene on the Y chromosome in the therians placental mammals and marsupials. Not all male-specific genes are located on the Y chromosome. Platypusa monotremeuse five pairs of different XY chromosomes with six groups of male-linked genes, AMH being the master switch. Birds and many insects have a similar system of sex determination ZW sex-determination systemin which it is the females that are heterogametic ZWwhile males are homogametic ZZ.

    Many insects of the order Hymenoptera instead have a system the haplo-diploid sex-determination systemwhere the males are haploid individuals which have just one chromosome of each typewhile the females are diploid with chromosomes appearing in pairs.

    Some other insects have the X0 sex-determination systemwhere just one chromosome type appears in pairs for the female but alone in the males, while all other chromosomes appear in pairs in both sexes.

    It has long been believed that the female form was the default template for the mammalian fetuses of both sexes. After the discovery of the testis-determining gene SRYmany scientists shifted to the theory that the genetic mechanism that causes a fetus to develop into a male form was initiated by the SRY gene, which was thought to be responsible for the production of testosterone and its overall effects on body and brain development.

    This perspective still shares the classical way of thinking; that in order to produce two sexes, nature has developed a default female pathway and an active pathway by which male genes would initiate the process of determining a male sex, as something that is developed in addition to and based on the default female form. However, In an interview for the Rediscovering Biology website, [11] researcher Eric Vilain described how the paradigm changed since the discovery of the SRY gene:.

    For a long time we thought that SRY would activate a cascade of male genes. It turns out that the sex determination pathway is probably more complicated and SRY may in fact inhibit some anti-male genes. The idea is instead of having a simplistic mechanism by which you have pro-male genes going all the way to make a male, in fact there is a solid balance between pro-male genes and anti-male genes and if there is a little too much of anti-male genes, there may be a female born and if there is a little too much of pro-male genes then there will be a male born.

    We [are] entering this new era in molecular biology of sex determination where it's a more subtle dosage of genes, some pro-males, some pro-females, some anti-males, some anti-females that all interplay with each other rather than a simple linear pathway of genes going one after the other, which makes it very fascinating but very complicated to study.

    In mammals, including humans, the SRY gene is responsible with triggering the development of non-differentiated gonads into testes, rather than ovaries. However, there are cases in which testes can develop in the absence of an SRY gene see sex reversal. In these cases, the SOX9 gene, involved in the development of testes, can induce their development without the aid of SRY. Even so, the absence of the SRY gene or the silencing of the SOX9 gene are not enough to trigger sexual differentiation секс a fetus in the female direction.

    A recent finding suggests that ovary development and maintenance is an active process, [12] regulated by the expression of a "pro-female" gene, FOXL2.

    In an interview [13] for the TimesOnline edition, study co-author Robin Lovell-Badge explained the significance of the discovery:. We take it for granted that we maintain the sex we are born with, including whether we have testes or ovaries. But this work shows that the activity of a single gene, FOXL2, is all that prevents adult ovary cells turning into cells found in testes.

    Looking into the genetic determinants of human sex can have wide-ranging consequences. Scientists have been studying different sex determination systems in fruit flies and animal models to attempt an understanding of how the genetics of sexual differentiation can influence biological processes like reproduction, ageing [14] and disease.

    In humans and many other species of animals, the father determines the sex of the child. In the XY sex-determination system, the секс ovum секс an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female XX or male XY offspring, respectively.

    Hormone levels in the male parent affect the sex ratio of sperm in humans. Human ova, like those of other mammals, are covered with a thick translucent layer called the zona pellucidawhich the sperm must penetrate to fertilize the egg. Секс viewed simply as an impediment to fertilizationrecent research indicates the zona pellucida may instead function as a sophisticated biological security system that chemically controls the entry of the sperm into the egg and protects the fertilized egg from additional sperm.

    Recent research indicates that human ova may produce a chemical which appears to attract sperm and influence their swimming motion. However, not all sperm are positively impacted; some appear to remain uninfluenced and some actually move away from the egg. Maternal influences may also be possible that affect sex determination in such a way as to produce fraternal twins equally weighted between one male and one female. The time at which insemination occurs during the estrus cycle has been found to affect the sex ratio of the offspring of humans, cattle, hamsters, and other mammals.

    Sex-specific mortality of embryos also occurs. Aristotle believed that the sex of an infant is determined by how much heat a man's sperm had during insemination. He wrote:. If, then, the male element prevails it draws the female element into itself, but if it is prevailed over it changes into the opposite or is destroyed. Aristotle claimed that the male principle was the driver behind sex determination, [19] such that if the male principle was insufficiently expressed during reproduction, the fetus would develop as a female.

    Nettie Stevens and Edmund Beecher Wilson are credited with independently discovering, inthe chromosomal XY sex-determination system, i. The first clues to the existence of a factor that determines the development of testis in mammals came from experiments carried out by Alfred Jost[23] who castrated embryonic rabbits in utero and noticed that they all developed as female.

    InC. Ford and his team, in the wake of Jost's experiments, discovered [24] that the Y chromosome was needed for a fetus to develop as male when they examined patients with Turner's syndromewho grew up as phenotypic females, and found them to be X0 hemizygous for X and no Y. All these observations lead to a consensus that a dominant gene that determines testis development TDF must exist on the human Y chromosome.

    From Wikipedia, the free encyclopedia. Pollen cones of a male Ginkgo biloba tree, a dioecious species. Main article: Sex determination system. Snake Sex Determination Dogma Overturned. March 4, Archived from the original on Larry; Loscalzo, Joseph Harrison's Principles of Internal Medicine 17th ed. McGraw-Hill Medical. Utrecht University - Department of Biology. Ultrecht, Netherlands. Archived PDF from the original on 27 November Retrieved 13 November Life Sci. Bibcode : Natur. February Archived from the original on 5 February Retrieved 3 May Henriette; et al.

    Journal of Biology. Biological Reviews. Jones and Kristin H. June Stevens and the Discovery of Sex Determination by Chromosomes". Retrieved Heilbron ed.

    Larsen's human embryology 4th ed. Sex determination and differentiation. Sexual differentiation humans Development of the reproductive system gonads Mesonephric duct Paramesonephric duct.

    Hermaphrodite Intersex Disorders of sex development Sex reversal. Development of the reproductive system. Development of the gonads Gonadal ridge Pronephric duct Mesonephric duct Paramesonephric duct Vaginal plate Definitive urogenital sinus. List of related male and female reproductive organs Prenatal development Embryogenesis.

    SRY, a gene cloned from the sex-determining region of the human Y identify and clone related genes from the Y chromosome of two marsupial species. Francine E. Brennan,; Gregory K. Hampikian,; Peter N. Goodfellow. MinoRuty anoup And sex EL Eco Ric compan its AMC syst EMs, st c EMPLovets *ALE FEMALE FFMALt Minor i: Y Mau E F EMALE at ack *AL E FEMALE. Muitos exemplos de traduções com "want to have sex with y" – Dicionário inglês-​português e busca em milhões de traduções.

    Linguee Apps

    Y Marks the Spot
    98club.info

    DeepL Translator Linguee. Open menu. Blog Press Information Linguee Apps. I would appeal to the President and Vice-Presidents to use their gavel to effect, so that. I have spoken out clearly in our dealings with Russia, and I stated, and I am секс out the English: we will use the regular dialogue that we have with Russia to discuss how to proceed'. In the Altmark judgement the Court of Justice set up four conditions w hi c h have to b e c omp li e d with i n o rder for such compensation to escape classification as State aid in a particular case 6.

    In the Altmark judgement the Court of Justice set up four conditions which have to be complied with in order for such compensation секс escape classification as State aid in a particular case 6. Poderia ser. It could be. Climate, Mr Davies, is what we a l l have to p u t u p with. Climate, Mr Davies, is what we all have to put up with. And no matter where the shipment takes place, you'll on l y have to d ea l with y o ur local claim handling center. And no matter where the shipment takes place, you'll only have to deal with your local claim handling center.

    If this e-mail has been forwarded to you and you wish to receive a monthly Meditation Focus and such occasional Peace Vigils, simply send an email to globalvisionary earthrainbownetwork.

    Near the секс of the story, Melvin says to Carol in one of the most beautiful lines in movie history:. On the other hand, you might n o t want a n yo ne el s e to have s u ch privileges.

    On the other hand, you might not want anyone else to have such privileges. Play time Now you are ready to play with the Debian system without risks as long as you use секс non-privileged user account.

    I supported the joint resolution put forward for that reason, b u t want to p u t on record my opposition to the concept of a European civil protection force. I supported the joint resolution put forward for that reason, but want to put on record my opposition to the секс of секс European civil protection force. These reforms are good in their own right, but, those of us who say in this Parliamen t w e want a c ce ssion : w e have to m секс ke their pain worthwhile by ourselves doing what we say, opening and closing chapters on merit, delivering the promises of the Council, ourselves acting in good faith.

    These reforms are good in their own right, but, those of us who say in this Parliament we want accession: we have to make their pain worthwhile by ourselves doing what we say, opening and closing chapters on merit, delivering the promises of the Council, ourselves acting in good faith. Decore o bolo com rosas, cerejas, frutas cristalizadas or whatever y o u want to. Garnish the cake with roses, cherries, dried fruits or whatever you want to.

    The news is the cover of "Tonight I want to cry", song by Keith Urban. Take it from me, as a person from Wales in the United Kingdom, we just do n o t want T u rk секс y to j o in. Take it from me, as a person from Wales in the United Kingdom, we just do not want Turkey to join. Department of State. Kutchera, a Milwaukee native, considered writing a book about this compelling trend as far back as Citi ze n s want to b e i nformed early on eur-lex. Citizens want to be informed early on eur-lex.

    Manual matches are great to organize the matches y o u want to p l ay yourself. Manual matches are great to organize the matches you want to play yourself. This is the way to underpin the reform s w e want to s e e happening in this valuable democratic neighbours of ours. This is the way to underpin the reforms we want to see happening in this valuable democratic neighbours of ours.

    Obviously, it is up to individual diaspora members to decide whether and how th e y want to g e t involved. Obviously, it is up to individual diaspora members to decide whether and how they want to get involved.

    To change the size, go to the message "What size do you want fonts to be? Its unique "autobypass" feature will automatically change disk navigation to eliminate pauses in playback by "jumping over" the removed parts of the секс directly to material you want to see. To apply for an openSUSE membership, head over to users. If we do n o t want t h e citi ze n s to d e se rt once more the European elections inpolitical leaders need to regain the citizens' trust and confidence in the European project and show they care about citizens' involvement in the decision-making machine.

    If we do n ot want th e citizens to desert once more the European elections inpolitical leaders need to regain the citizens' trust and confidence in the European project and show they care about citizens' involvement in the decision-making machine.

    Estamos agradecidos pelo seu voto! I would appeal to the President секс Vice-Presidents to use their gavel to effect, so that [ Poderia ser [ It could be [ Near the end of the story, Melvin says to Carol in one of the most beautiful lines in movie history: [ Kutchera, [

    Molecular Ecology Some organisms, such as bacteria, contain just a single cell. Diploid individuals are generally female but may be sterile males. sex dating

    All males are about That means that any two males differ by only 0. And even as women continue to fight for equality in many aspects of society today, they are less like men than even Jefferson knew, sharing only David C. Page, Director of the Севс Institute and a Professor of Biology at the Massachusetts Institute of Technology, referring to секс way in which the genetic code is translated by the body when creating proteins, the building blocks of cells.

    Life on our planet began with single-cell organisms such as bacteria that reproduce asexually. A cell simply reproduces its genetic material and divides into two or more cells that are genetically identical to the parent cell. About three or four billion years ago, these single-cell organisms without a distinct nucleus prokaryotes, or bacteria began exchanging genetic information in a limited fashion.

    Then about two billion years ago, organisms such as yeast, with distinct cellular nuclei and specialized structures called organelles eukaryotesput their genes in pairs so that they could be divided into two structurally identical gametes one-cell reproductive units called spores in the case секс yeast and reassembled to create a new organism. This снкс kind of cell division is called meiosis.

    Around million years ago, animals began to evolve specialized gametes — structurally different single-cell units for females eggs and males sperm.

    Sperm cells fertilize an egg, which then combines the genes of both parents. But such animals, including modern-day turtles, had no specialized sex chromosomes that determine the sex of the offspring. Males and females were genetically identical, and the sex was determined by the temperature at which the egg is incubated. And finally, starting about million years ago, our ancestors began to evolve sex chromosomes. In humans, there are 23 pairs of chromosomes, which are structures found within the nucleus of every cell containing the tightly packed molecules known as deoxyribonucleic acid DNAthe material that carries the genetic code.

    One pair of the 23 chromosomes, known as sex chromosomes, determines at conception whether a fertilized egg will develop into a male or female. Today, human females have one pair of identical X chromosomes. Human males, instead of a matched pair, have one X and one smaller Y chromosome. A human egg contains only an X chromosome. A human sperm contains either ee X or a Y chromosome, thereby determining the sex of the offspring after fertilization. Page and his colleagues have spent the better part of the last two decades reconstructing the evolutionary origins of the human X and Y chromosomes.

    They have traced the origins of these sex chromosomes to ordinary chromosomes called autosomes in evolutionary ancestors that humans share with birds.

    Most of them are on the autosomes. They are exactly the same in males and females. Eventually a mutation arose on a member of one of these ordinary pairs of chromosomes that became what lives on today as the sex-determining gene on the Y chromosome known as SRY.

    Then, Page said, first in the immediate vicinity of SRY and then over a larger region, what were slowly becoming the X and Y chromosomes stopped swapping information. The X chromosome continued to trade genetic information with other X chromosomes through female meiosis.

    But during male meiosis, the Y became isolated. And damaging mutations that would have ordinarily been purged through the natural sharing process began to accumulate, leaving the Y chromosome smaller and with fewer surviving genes from that earlier ancestor.

    Today, the human X chromosome retains of these ancestral genes. The Y chromosome only has 17 survivors, all of which also continue to survive on сек X. And these genes did not just survive all that time in species that eventually evolved into humans. Additional research revealed that the surviving human genes had special qualities, Page said. Those that survived on the Y chromosome are broadly expressed active in many tissues and organs throughout the body in both adult tissues and in embryos prior to implantation.

    Of the 17 surviving genes on the Y chromosome, 12 are expressed widely across the body, not just in the testes, where sperm are produced, Page said. Many play central roles in the execution of gene regulation and expression. Page called for medical schools to ссекс the differences between XX and XY cells at a more fundamental level.

    For the last 50 years, students have been taught that outside the gonads — reproductive organs where sperm and eggs are produced — cells with XX and XY pairs are functionally equivalent because there is nothing сеус the Y chromosome that acts outside the testes. But Page argued that there are intrinsic biochemical differences between XX and XY cells that affect tissues and organs across the entire body and d a significant impact independent of sex hormones.

    And medical practitioners must understand these differences чекс properly treat their patients. Page points to dilated cardiomyopathy, a genetic defect in which the heart balloons dangerously and kills men an average of 10 years earlier than women. Or how there are about three times as many women than men with rheumatoid arthritis and as many as five times the number of boys diagnosed with autism as there are girls.

    Of those who suffer from the autoimmune disorder lupus, 90 percent are women. Because there are no obvious anatomical distinctions accounting for these and many other differences, Page urges researchers to examine how XX and XY cells work differently throughout the body. But he remained optimistic, even as he proposed the restructuring of medical science to finally grapple with overlooking for too long the most fundamental секв between men and women.

    A new секс to better understand the nature of what it means to be male and female. For more news from Women's Health Research at Yale, sign up for our e-blastsconnect with секс on Facebook and Twitteror visit our website.

    For questions, please contact Rick Harrison, Communications Officer, at or rick. Cell: The smallest structural unit of a living organism, cells are microscopic and possess the ability to replicate independently. Some organisms, such as bacteria, contain just a single cell. Humans have more than 10 trillion cells, which combine to form сеск, such as muscle, and organs, such as the heart.

    DNA: Deoxyribonucleic acid, a self-replicating material that carries the genetic code of almost all living things and directs the production of proteins, the building blocks of cells. Gene: A part of the DNA molecule that forms the basis of heredity, passing traits such as спкс color, hair type, and freckles from parents to offspring.

    Humans have somewhere between 20, and 25, genes. Expression: The process by which a gene leads to the appearance of a particular characteristic or effect of that gene.

    Mutation: A change in секс sequence of DNA created through replication error or unrepaired секс. Mutations that help a species reproduce and survive in greater numbers drive evolution, the process by which organisms change over time. Humans have a секс of 46 chromosomes in 23 pairs. Out of 23 pairs of chromosomes, human females have one pair of identical X chromosomes.

    Human males, instead of a matched pair, have one X and one Y chromosome. Autosome: A chromosome that is сккс a sex chromosome. Humans have 22 pairs of autosomes and one pair of sex chromosomes.

    Genome: The complete set of genes or genetic material present in a cell or organism. PAGE Dr. Page drapes a Yale t-shirt over a podium and jokes of his particular comfort on the "Y" logo-friendly Yale campus before delivering a lecture. REALITY Medical students секс taught that X and Y chromosomes have no impact on cells outside of the reproductive organs — that sex hormones are entirely responsible for making the body more masculine or feminine. But Dr. Page argues that there are секв between XX and XY cells that affect tissues and organs across the entire body.

    Thomas Jefferson declared that all men are created equal, and he was mostly correct. Submitted by Carissa R Violante on August 30, Your browser is antiquated and no longer supported on this website.

    Please update your browser or switch to Chrome, Firefox or Сес.

    Join for Free Now!

    This member says 98club.info is her favorite of all sex sites for adult dating

    Article metrics
    Nude Cam Chat

    Wanna chat online?

    Thank you for visiting nature. You are using a browser version with limited support for CSS. Секс obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Help us improve our products. Sign up to take part. A Nature Research Journal. IN mammals, testis determination is under the control of the testis-determining factor borne by the Y chromosome 1,2.

    SRYa gene cloned from the sex-determining region of the human Y chromosome, has been equated with the testis-determining factor in man 3—5 and mouse 6,7. We have used a human SRY probe to identify and clone related genes секс the Y chromosome of two marsupial species. The SRY homologues, секс with the mouse Ubely homologues 8are the first genes to be identified on the marsupial Y chromosome.

    Jost, A. Ford, C. Lancet i Sinclair, A. Nature— Berta, P. Jager, R. Gubbay, J. Koopman, P. Mitchell, M. Nature this issue. Hope, R. O Wai-Sum, Short, R. Sharman, G. Page, D. Cell 51— Nasrin, Секс. Denny, P. Nucleic Acids Res. Griffiths, R. B— Harley, V. Science— Hawkins, J. Sambrook, J. Sanger, F. Download references. Reprints and Permissions. Foster, J. Evolution of sex determination and the Y chromosome: SRY -related sequences in marsupials.

    Nature— doi Download citation. Reproduction, Fertility and Development BMC Biology BMC Секс Journal of Phycology Molecular Ecology секс By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our секс or guidelines please flag it as inappropriate.

    Advanced search. Skip to main content. Subscribe Search My Account Login. Abstract IN mammals, testis determination is under the секс of the testis-determining factor borne by the Y chromosome 1,2.

    Access through your institution. Buy or subscribe. Change institution. Rent or Buy article Get time limited or full article access on ReadCube. References 1 Jost, A. Article Google Scholar 3 Sinclair, A. Article Google Scholar 12 Page, D. Google Scholar 20 Sanger, F. Author information Author notes Jamie W. Sinclair Authors Search for Jamie W.

    Rights and permissions Reprints and Permissions. About this article Cite this article Foster, J. Further reading Marsupial genomics meet marsupial reproduction Jennifer A. OrtegaNathan J. O'Neill Molecular Ecology Comments By submitting a comment you agree to abide by секс Terms and Community Guidelines. Nature menu. Nature Research menu.

    Search Article search Search. Newsletter Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing. Close banner Close.

    Profile page view of 98club.info member looking for one night stands

    AFF®

    1, online suppl. fig. 3). (E) Sex reversal by translocation of the SRY gene to the X chromosome resulting in a neo-Y through local recombination. Muitos exemplos de traduções com "want to have sex with y" – Dicionário inglês-​português e busca em milhões de traduções. Dr. David C. Page discusses the origin of the X and Y chromosomes and sign up for our e-blasts, connect with us on Facebook and Twitter.

    Register for free now!

    Any Device

    Sex-determination system - WikipediaEvery Cell Has a Sex: X and Y and the Future of Health Care < Yale School of Medicine

    A sex-determination system is a biological system that determines the development of sexual characteristics in an organism.

    Most organisms that create their offspring using sexual reproduction have two sexes. Occasionally, there are hermaphrodites in place of one or both sexes. There are also some species that are only one sex due to parthenogenesisthe act of a female reproducing without fertilization.

    In many species, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology.

    The sexual differentiation is generally triggered by a main gene a "sex locus"with a multitude of other genes following in a domino effect. In other cases, sex of a fetus is determined by environmental variables such as temperature. The details of some sex-determination systems are not yet fully understood. Hopes for future fetal biological system analysis include complete-reproduction-system initialized signals that can be measured during pregnancies to more accurately determine whether a determined sex of a fetus is male, or female.

    Such analysis of biological systems could also signal whether the fetus is hermaphrodite, which includes total or partial of both male and female reproduction organs. Some species such as various plants and fish do not have a fixed sex, and instead go through life cycles and change sex based on genetic cues during corresponding life stages of their type. This could be due to environmental factors such as seasons and temperature. Human fetus genitals can sometimes develop abnormalities during maternal pregnancies due to mutations in the fetuses sex-determinism system, resulting in the fetus becoming intersex.

    Sex determination was discovered in the mealworm by the American geneticist Nettie Stevens in In this system, most females have two of the same kind of sex chromosome XXwhile most males have two distinct sex chromosomes XY. The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes autosomesand are sometimes called allosomes.

    In some species, such as humans, organisms remain sex indifferent for a time after they're created; in others, however, such as fruit flies, sexual differentiation occurs as soon as the egg is fertilized.

    Some species including humans have a gene SRY on the Y chromosome that секс maleness. In Y-centered sex determination, the SRY gene is the main gene in determining male characteristics, but multiple genes are required to develop testes.

    In XY mice, lack of the gene DAX1 on the X chromosome results in sterility, but in humans it causes adrenal hypoplasia congenita. Some species, such as fruit fliesuse the presence of two X chromosomes to determine femaleness.

    Some fish have variants of the XY sex-determination systemas well as the regular system. For example, while having an XY format, Xiphophorus nezahualcoyotl and X. At least one monotremethe platypuspresents a particular sex determination scheme that in some ways resembles that of the ZW sex chromosomes of birds and lacks the SRY gene.

    Although it is an Секс system, the platypus' sex chromosomes share no homologues with eutherian sex chromosomes. However, homologues to the avian DMRT1 gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination. More research must be conducted in order to determine the exact sex determining gene of the platypus.

    In this variant of the XY system, females have two copies of the sex chromosome XX but males have only one X0. The 0 denotes the absence of a second секс chromosome. Generally in this method, the секс is determined by amount of genes expressed across the two chromosomes. This system is observed in a number of insects, including the grasshoppers and crickets of order Orthoptera and in cockroaches order Blattodea. A small number of mammals also lack a Y chromosome.

    These include the Amami spiny rat Tokudaia osimensis and the Tokunoshima spiny rat Tokudaia tokunoshimensis and Sorex araneusa shrew species. Transcaucasian mole voles Ellobius lutescens also have a form of XO determination, in which both sexes lack a second sex chromosome.

    The nematode C. These genes reduce male gene activation and increase it, respectively. The ZW sex-determination system is found in birds, some reptiles, and some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes ZWand males have two of the same kind of chromosomes ZZ. In the chicken, this was found to be dependent on the expression of DMRT1.

    In the case of the chicken, their Z chromosome is more similar to humans' autosome 9. This is due to the fact that the haploid eggs double their chromosomes, resulting in ZZ or WW. The ZZ become males, but the WW are not viable and are not brought to term. In some Bryophyte and some algae species, the gametophyte stage of the life cycle, rather than being hermaphrodite, occurs as separate male or female individuals that produce male and female gametes respectively.

    When meiosis occurs in the sporophyte generation of the life cycle, the sex chromosomes known as U and V assort in spores that carry either the U chromosome and give rise to female gametophytes, or the V chromosome and give rise to male gametophytes.

    Haplodiploidy is found in insects belonging to Hymenopterasuch as ants and bees. Unfertilized eggs develop into haploid individuals, which are the males. Diploid individuals are generally female but may be sterile males.

    Males cannot have sons or fathers. This may be significant for the development of eusocialityas it increases the significance of kin selectionbut it is debated. This allows them to create more workers, depending on the status секс the colony. Many other sex-determination systems exist. In some species секс reptiles, including alligatorssome turtlesand the tuatarasex is determined by the temperature at which the egg is incubated during a temperature-sensitive period.

    There are no examples of temperature-dependent sex determination TSD in birds. Megapodes had formerly been thought to exhibit this phenomenon, but were found to actually have different temperature-dependent embryo mortality rates for each sex.

    The specific temperatures required to produce each sex are known as the female-promoting temperature and the male-promoting temperature. It is unknown how exactly temperature-dependent sex determination evolved. For example, a секс area could be more suitable for nesting, so more females are produced to increase the amount that nest next season. There are other environmental sex determination systems including location-dependent determination systems as seen in the marine worm Bonellia viridis — larvae become males if they make physical contact with a female, and females if they end up on the bare sea floor.

    This is triggered by the presence of a chemical produced by the females, bonellin. In tropical clown fishthe dominant individual in a group becomes female while the other ones are male, and bluehead wrasses Thalassoma bifasciatum are the reverse. Some species, however, have no sex-determination system. Hermaphrodite species include the common earthworm and certain species of snails.

    A few species of fish, reptiles, and insects reproduce by parthenogenesis and are female altogether. There are some reptiles, such as the boa constrictor and Komodo dragon that can reproduce both sexually and asexually, depending on whether a mate is available. Other unusual systems include those of the swordtail fish [ clarification needed ] ; [11] the Chironomus midges [ clarification needed ] [ citation needed ] ; the platypuswhich has 10 sex chromosomes [12] but lacks the mammalian sex-determining gene SRY, meaning that the process of sex determination in the platypus remains unknown; [13] the juvenile hermaphroditism of zebrafishwith an unknown trigger; [11] and the platyfishwhich has W, X, and Y chromosomes.

    The accepted hypothesis of XY and ZW sex chromosome evolution is that they evolved at the same time, in two different branches. All sex chromosomes started out as an original autosome of an original amniote that relied upon temperature to determine the sex of offspring.

    After the mammals separated, the branch further split into Lepidosauria and Archosauromorpha. These two groups both evolved the ZW system separately, as evidenced by the existence of different sex chromosomal locations. The regions of the X and Y chromosomes that are still homologous to one another are known as the pseudoautosomal region. There are some species, such as the medaka fish, that evolved sex chromosomes separately; their Y chromosome never inverted and can still swap genes with the X.

    These species' sex chromosomes are relatively primitive and unspecialized. From Wikipedia, the free encyclopedia. A biological system that determines the development of sexual characteristics in an organism.

    Main article: XY sex-determination system. Main article: X0 sex-determination system. Main article: ZW sex-determination system. Main article: Haplodiploidy. Main article: Temperature-dependent sex determination. Further information: Environmental sex determination. Retrieved 7 June Proceedings of the American Philosophical Society.

    Секс Education. Retrieved 8 December Cellular and Molecular Life Sciences. Current Science. New England Journal of Medicine. American Journal of Medical Genetics. Секс and Molecular Biology.

    Mechanisms of Development. Bibcode : Natur. Ashley; D. Graves Chromosome Res. Kuwabara; Peter G. Okkema; Judith Kimble April Molecular Biology of the Cell. September Genome Res.