User:Alexis Skipper/Testis-determining factor

(In bold is what I have changed or added to the section titled "Influence on Sex")

Change section title from "Influence on Sex" to "SRY Disorders Influence on Sex Expression"

Embryos are gonadally identical, regardless of genetic sex, until a certain point in development when the testis-determining factor causes male sex organs to develop. A typical male karyotype is XY, whereas a females is XX. '''There are exceptions, however, in which SRY plays a major role. Individuals with Klinefelter syndrome inherit a normal Y chromosome and multiple X chromosomes, giving them a karyotype of XXY. These persons are considered male . Atypical genetic recombination during crossover, when a sperm cell is developing,''' can result in karyotypes that do not match their phenotypic expression.

Most of the time, when a developing sperm cell undergoes crossover during meiosis, the SRY gene stays on the Y chromosome. Nonetheless, if the SRY gene is transferred to the X chromosome instead of staying on the Y chromosome, testis development will no longer occur. This is known as Swyer syndrome, characterized by an XY karyotype and a female phenotype. '''Individuals who have this syndrome have normally formed uteri and fallopian tubes, but the gonads are not functional. Swyer syndrome individuals are generally raised as females and have a female gender identity . On the other spectrum, XX male syndrome occurs when a body has female chromosomes and SRY attaches to one of them through translocation. People with XX male syndrome have female genotype but male physical features . Individuals with either of these syndromes can experience delayed puberty, infertility, and growth features of the opposite sex they identify with. XX male syndrome expressers may develop breast, and those with Swyer syndrome may have facial hair .'''

While the presence or absence of SRY has generally determined whether or not testis development occurs, it has been suggested that there are other factors that affect the functionality of SRY. Therefore, there are individuals who have the SRY gene, but still develop as females, either because the gene itself is defective or mutated, or because one of the contributing factors is defective. This can happen in individuals exhibiting a XY, XXY, or XX SRY-positive karyotype.

Additionally, other sex determining systems that rely on SRY/TDF beyond XY '''are the processes that come after SRY is present or absent in the development of an embryo. In a normal system, if SRY is present for XY, the TDF will activate the medulla to develop gonads into testes. Testosterone will then be produced and initiate the development of other male sexual characteristics. Comparably, if SRY is not present for XX, there will be a lack of the TDF based off no Y chromosome. The lack of TDF will allow the cortex of embryonic gonads to develop in to ovaries, which will then produce estrogen, and lead to the development of other female sexual characteristics .'''