The XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants. In this system, the sex of an individual is determined by a pair of sex chromosomes. Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two different kinds of sex chromosomes (XY), and are called the heterogametic sex.
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 common sexes and a few less common intersex variations.
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining because it is the presence or absence of Y chromosome that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads. The Y chromosome is passed only from male parents to male offspring.
XY gonadal dysgenesis, also known as Swyer syndrome, is a type of defect hypogonadism in a person whose karyotype is 46,XY. Though they typically have normal vulvas, the person has underdeveloped gonads, fibrous tissue termed "streak gonads", and if left untreated, will not experience puberty. The cause is a lack or inactivation of an SRY gene which is responsible for sexual differentiation. Pregnancy is often possible in Swyer syndrome with assisted reproductive technology. The phenotype is usually similar to Turner syndrome (45,X0) due to a lack of X inactivation. The typical medical treatment is hormone replacement therapy. The syndrome was named after Gerald Swyer, an endocrinologist based in London.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
Sex-determining region Y protein (SRY), or testis-determining factor (TDF), is a DNA-binding protein encoded by the SRY gene that is responsible for the initiation of male sex determination in therian mammals. SRY is an intronless sex-determining gene on the Y chromosome. Mutations in this gene lead to a range of disorders of sex development with varying effects on an individual's phenotype and genotype.
XX male syndrome, also known as de la Chapelle syndrome, is a rare congenital intersex condition in which an individual with a 46,XX karyotype develops a male phenotype. Synonyms include 46,XX testicular difference of sex development, 46,XX sex reversal, nonsyndromic 46,XX testicular DSD, and XX sex reversal.
Ovotesticular syndrome is a term for an intersex condition in which an individual is born with both ovarian and testicular tissue. Commonly, one or both gonads is an ovotestis containing both types of tissue. Although it is similar in some ways to mixed gonadal dysgenesis, the conditions can be distinguished histologically.
XX gonadal dysgenesis is a type of female hypogonadism in which the ovaries do not function to induce puberty in an otherwise normal girl whose karyotype is found to be 46,XX. With nonfunctional streak ovaries, she is low in estrogen levels (hypoestrogenic) and has high levels of FSH and LH. Estrogen and progesterone therapy is usually then commenced. Some cases are considered a severe version of premature ovarian failure where the ovaries fail before puberty.
Gonadal dysgenesis is classified as any congenital developmental disorder of the reproductive system in humans. It is atypical development of gonads in an embryo. One type of gonadal dysgenesis is the development of functionless, fibrous tissue, termed streak gonads, instead of reproductive tissue. Streak gonads are a form of aplasia, resulting in hormonal failure that manifests as sexual infantism and infertility, with no initiation of puberty and secondary sex characteristics.
Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts and body hair plays a role in sex identification.
Pseudohermaphroditism is a condition in which an individual has a matching chromosomal and gonadal tissue sex, but mismatching external genitalia.
Disorders of sex development (DSDs), also known as variations in sex characteristics (VSC), are congenital conditions affecting the reproductive system, in which development of chromosomal, gonadal, or anatomical sex is atypical.
The southern mole vole is a species of rodent in the family Cricetidae. It is found in Afghanistan, Iran, Pakistan, and Turkmenistan.
The Transcaucasian mole vole is a species of rodent in the family Cricetidae.
The northern mole vole is a species of rodent in the family Cricetidae. It is distributed over large parts of Eastern Europe and Asia.
An ovotestis is a gonad with both testicular and ovarian aspects. In humans, ovotestes are an infrequent anatomical variation associated with gonadal dysgenesis. The only mammals where ovotestes are not symptomatic of an intersex variation are moles, wherein females possess ovotestes along with a masculinized clitoris. These ovotestes in nonpregnant female moles secrete eight times as much testosterone as the ovotestes of pregnant moles. In invertebrates that are normally hermaphroditic, such as most gastropods in the clade Eupulmonata, an ovotestis is a common feature of the reproductive anatomy.
Transcription factor SOX-9 is a protein that in humans is encoded by the SOX9 gene.
Forkhead box protein L2 is a protein that in humans is encoded by the FOXL2 gene.
R-spondin-1 is a secreted protein that in humans is encoded by the RSPO1 gene, found on chromosome 1. In humans, it interacts with WNT4 in the process of female sex development. Loss of function can cause female to male sex reversal. Furthermore, it promotes canonical WNT/β catenin signaling.
