SRY gene

Also known as testis-determining factor.


The sex-determining region Y (SRY) protein, is a DNA-binding protein encoded by the SRY gene that is responsible for the initiation of male sex determination in mammals.



SRY is an intronless sex-determining gene on the Y chromosome.



Mutations in this gene is associated with disorders of sex development and with varying effects on an individual’s phenotype and genotype.



Gene location is the  Y chromosome.



The  SRY gene is located on short (p) arm of the Y chromosome at position 11.2



Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. 



Primary sex cords form in the undifferentiated gonad, turns it into a testis. 



The Leydig cells of the testis secrete testosterone, while the Sertoli cells produce anti-Müllerian hormone.



SRY gene effects normally take place 6–8 weeks after fetus formation.



SRY gene inhibits the female anatomical structural growth in males,and works to develop the dominant male characteristics.



SRY is one of only four genes on the human Y chromosome that have arose from the original Y chromosome.



Mutations in the SRY region result in sex reversal, where the opposite sex is produced.



Deletion of the gene results  in complete sex reversal. 



During gestation, the primordial gonad cells that lie along the urogenital ridge possess the ability to become either male cells (Sertoli and Leydig cells) or female cells (follicle cells and theca cells). 



Testicle determining factor initiates testis differentiation by activating male-specific transcription factors that allow these bipotential cells to differentiate and proliferate. 



Testicle determining factor upregulates SOX9, a transcription factor which leads to the upregulation of fibroblast growth factor 9 (Fgf9), which in turn leads to further upregulation of SOX9. 



When SOX9 levels are reached, the bipotential cells of the gonad begin to differentiate into Sertoli cells. 



Cells expressing testicle determining factor (TDF) continue to proliferate to form the primordial testis. 



SOX9 and TDF are responsible for the cell-autonomous differentiation of cell precursors in the gonads into Sertoli cells, the beginning of testes development. 



Embryos are gonadally identical, regardless of genetic sex.



At a certain point in development when the testis-determining factor causes male sex organs to develop.



SRY plays a major role in patients with Klinefelter syndrome that inherit a normal Y chromosome and multiple X chromosome, these persons are considered male.



Such atypical genetic recombinations can result in karyotypes that do not match their phenotypic expression.



When a developing sperm cell undergoes crossover during meiosis, the SRY gene usually stays on the Y chromosome. 



If the SRY gene is transferred to the X chromosome instead of staying on the Y chromosome, testis development will no longer occur (Swyer syndrome).



((Swyer syndrome)) is characterized by an XY karyotype and a female phenotype. 



With Swyer syndrome women have normally formed uteri and fallopian tubes, but the gonads are not functional. 



Swyer syndrome individuals are raised as females and have a female gender identity.



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 XY, XX 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.



Inherit a normal Y chromosome and multiple X chromosomes, giving persons a karyotype of XXY.



Persons with XXY  are considered male


Swyer Syndrome.



SRY gene is transferred to the X chromosome instead of staying on the Y chromosome: testis development will no longer occur.



The presence or absence of SRY determines whether or not testis development occur.



Individuals who have the SRY gene, but still develop as females, occurs  because the gene itself is defective or mutated, or because one of the contributing factors is defective: exhibiting a XY, XXY, or XX SRY-positive karyotype.



SRY gene interacts with the androgen receptor and individuals with XY karyotype and a functional SRY gene can have an outwardly female phenotype due to an underlying androgen insensitivity syndrome.



Androgen insensitivity syndrome (AIS) refers to individuals unable to respond to androgens properly due to a defect in their androgen receptor gene, and affected individuals can have complete or partial AIS.



SRY gene linked to males being more likely than females to develop dopamine-related diseases such as schizophrenia and Parkinson’s disease, as encodes a protein that controls the concentration of dopamine, the neurotransmitter that carries signals from the brain that control movement and coordination.


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