Sex Determining Region Y
In mammals, the X and Y-chromosomes determine the sex of an organism. If a mammal is homologous XX than that mammal will be female and if the mammal is heterozygous XY that individual will be male, assuming no mutations. What is it about the Y chromosome that dictates the male sex? On the short arm of the Y-chromosome is a region called the sex-determining region Y or SRY that codes for transcription factor “sex-determining Y” protein in mammals. In 1991, the function of SRY was revealed to be the sex-determining gene in mice that was responsible for testes formation. This was determined in a study where homologous XX mice (female) had been introduced to SRY and subsequently became male (Koopman et al. 1991).
SRY is part of the SOX transcription factor family. Like others in its family, SRY has a high mobility group or HMG DNA-binding domain which is about eighty amino acids long that is structurally related to other domains in the SOX family. The domain has a specific binding sequence, AACAAAG or AACAAT, that is binds to and a particular angle it bends at when it binds to the specific sequence, where both the sequence and the bending angle are crucial for function (Harley and Goodfellow 1994). In human females that are XY, many have mutations in the HMG domain, again supporting the importance of the domain sequence for function and when SRY is not expressed, genes express female-specific traits and induce ovarian development. (Harley and Goodfellow 1994).
Among animal species SRY, besides the HMG domain is not highly conserved and varies between species. Many studies involving SRY have used the mouse as a model. In an XY mouse embryo at 10 days post coitum or dpc, gonads arise from the genital ri...
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One of the major biological differences between males and females are hormones. Hormones that were once thought to only be important for pregnancy and sexual drive are now shown to have profound effects on just about every organ in the body.(*) Some researchers believe that higher exposure to estrogen, in females, or androgens, in males, during fetal development not only causes the sex organs to form but also predisposes the infant to behavior that is typically associated with one gender or the other. (*) For example, girls that were exposed to higher than normal prenatal levels of androgens were more likely than other females to engage in “boy-like” behavior and to play with boy’s toys eve...
Ross Wolff, Jennifer, and David Zarkower. "Somatic Sexual Differentiation in Caenorhabditis Elegans." Current Topics in Developmental Biology 83 (2008): 1-39. Web. 28 Feb. 2014. .
Swaab, Df. "Sexual Differentiation Of The Human Brain: Relevance For Gender Identity, Transsexualism And Sexual Orientation." Gynecological Endocrinology 19.6 (2004): 301-312. Informa Healthcare . Web. 7 Apr. 2014.
As you can see, it is important to research sexual selection across various species’. Similar mechanisms of selection are present in all animals. By learning how these mechanisms act in one species, it is possible to gain insight into the behavior of all animals, including human beings.
In order to test the hypothesis and ensure that other genes in the larger chromosome region were not the real cause of pelvic loss the scientists generated F1 hybrids between both pelvic-completed and pelvic-reduced sticklebacks as well as two pelvic-complete populations. These F1 hybrids allowed for combination of the alleles of Pitx1 from pelvic-complete (FRIL, LITC) and pelvic-reduced (PAXB) populations. Brain and pelvic tissues were isolated to compare the expression of either the LITC or PAXB allele to the FRIL allele. The results supported the initial hypothesis as expression of the PAXB Pitx1 allele was greatly reduced in the pelvis but not the head of F1 hybrids, indicating a tissue-specific, cis-regulatory change in the Pitx1 locus. If indeed other genes in the larger chromosome region were the real cause of pelvic reduction then there would have been a secondary or trans-acting reduction seen in the expressions of Pitx1 in both
Complete androgen insensitivity syndrome occurs when the body is unable to use androgens at all. Affected individuals with this form have the external sex characteristics of females, but do not have a uterus, will not menstruate, and are infertile. They also will not have axillary or pubic hair, or acne which is linked to puberty. Androgen insensitivity syndrome individuals develop internal male sex organs. Partial androgen insensitivity syndrome (Reifenstein syndrome) is when the body’s tissues are partially sensitive to the effects of androgens. Affected individuals can have normal female sex characteristics, both male and female sex characteristics, or normal male sex characteristics. An individual may be brought up as a male then u...
About half of a man’s testosterone is actually freely in circulation, or ‘biologically active’. The other half is bound to a globulin, called the sex h...
To begin with, gender must be examined at the basic level of science in regard to physical and biological development of humans. We all understand the physical differences between the male and female gender, but how is our sex actually determined. After conception,
Over the course of several years, evolutionists have tried to explain the actuality of sexual reproduction to promote genetic variability. However, this explanation is not only faulty but poses a few disadvantages as well. Sexual reproduction happens by the formation of g...
Gender is determined by the sex chromosomes, XX produces a female, and XY produces a male. Males are produced by the action of the SRY gene on the Y chromosome, which contains the code necessary to cause the indifferent gonads to develop as testes (1). In turn the testes secrete two kinds of hormones, the anti-Mullerian hormone and testosterone, which instruct the body to develop in a masculine fashion (1). The presence of androgens during the development of the embryo results in a male while their absence results by default in a female. Hence the dictum "Nature's impulse is to create a female" (1). The genetic sex (whether the individual is XX or XY) determines the gonadal sex (whether there are ovaries or testis), which through hormonal secretions determines the phenotypic sex. Sexual differentiation is not drive...
In this experiment, Mendelain Models are observed. The purpose of the experiment is to understand how traits are passed from one generation to the other as well as understanding the difference between sex linked and autosomal genes. One particular trait that is observed in this experiment is when a fly is lacking wings, also known as an apterous mutation. In this experiment, we will determine whether this mutation is carried on an autosomal chromosome or on a sex chromosome. The data for this experiment will be determined statistically with the aid of a chi-square. If the trait is autosomal, then it will be able to be passed to the next generation on an autosomal chromosome, meaning that there should be an equal amount of male and
You determine a human’s sex with the XY Sex-Determination System. All humans, most mammals, and a smattering of plants, insects, and reptiles become classified by the set of chromosomes that they’re born with. Females are homogametic (having the same sex chromosomes, XX), while males are heterogametic (have different chromosomes, XY). There are conditions where it is possible to have a different chromosome lineup than the typical two stated here. The most common is being intersex, happening 1 in 2000 births. If you’re intersex, then you were born with heterogametic chromosomes, but they both never became fully developed, meaning you could lose some of the typical male or female secondary sexual characteristics, i.e. pubic hair, enlarged Adam’s
The SRY gene is the initiator of sex determination and unless this gene is present all developing foetuses will be female. This is due to the high level of female hormones in the blood from the mother. It isn't until the Y chromosome is present with the SRY gene on it to degenerate the female tracts (Mullerian) and promote male tracts (Wolffian) by the release of anti-Mullerian substance and the stimulation of the Sertoli cells to secrete testosterone which leads to the release of hCG to stimulate the release of DHT to promote growth further and overcome the maternal hormones.
Most of today’s theorists and scientists have a different perception of determining whether or not gender can be based on biological factors, or evolutionary factors. Gender determination involving humans can be identified by evaluating male and female chromosomes. Theorist of Penn State (2005) contains that chromosomes is a combination of instructions used to produce organism. As previously stated, the male chromosomes consist of X and Y. These two chromosomes are responsible for creating male gender and their ability to produce sperm. The female egg consists of double XX chromosome. Based on this theory, the X chromosomes carry a more dominant instruction manual than the Y chromosome.
The X-chromosome is one of the two sex chromosomes(the other being Y) that is responsible for a variety of factors in a child’s developmental growth, the most commonly known being their biological sex. Researchers at the National Center for Biotechnology Information have studied the X-chromosome and its relation to homosexuality in men. Preceding their studies, the researchers hypothesized, “If the X Chromosome contains a gene that increases the probability of an individual’s being homosexual, then genetically related gay men should share X chromosome markers close to that gene. If no such gene exists, then no statistically significant correlations between sexual orientation and X chromosome will be observed” (Bocklandt, Horvath, Vilain, Hamer).