Swyer syndrome is a problem that affects sex development. Sex advance usually complies with a specific path based on an individual"s chromosomes; however, in Swyer syndrome, sex advance is not typical for the affected individual"s chromosomal pattern.
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People usually have 46 chromosomes in each cell. Two of the 46 chromosomes, recognized as X and Y, are referred to as sex chromosomes because they assist determine even if it is a human will develop male or woman sex characteristics. Girls and also women frequently have two X chromosomes (46,XX karyotype), when boys and also men generally have one X chromosome and also one Y chromosome (46,XY karyotype). In Swyer syndrome, individuals have actually one X chromosome and also one Y chromosome in every cell, which is the pattern generally found in boys and also men; however, they have actually female reproductive structures.
People through Swyer syndrome have female exterior genitalia and some female interior genitalia; the uterus and also fallopian tubes are normally-formed, yet the gonads (ovaries or testes) space not functional. Instead, the gonads are little and underdeveloped and contain tiny gonadal tissue. These structures are called streak gonads. The streak gonadal organization is at threat of developing hard-to-detect cancers, so that is usually removed surgically. Swyer syndrome is sometimes dubbed 46,XY finish gonadal dysgenesis; the medical term “dysgenesis” suggests that advance (in this condition, breakthrough of the gonads) is reduced and not typical.
People through Swyer syndrome are usually raised as girls and have a female gender identity. Swyer syndrome might be identified prior to birth, in ~ birth, or later on when a boy does not go through puberty as usual. Since they carry out not have functional ovaries that create hormones, influenced individuals often start hormone replacement therapy throughout adolescence to begin puberty, bring about the breasts and uterus come grow, and also eventually resulting in menstruation. Hormone replacement therapy also stimulates bone advancement and helps alleviate the risk of abnormally short bone thickness (osteopenia and also osteoporosis). Women through Swyer syndrome do not produce eggs (ova), yet they may have the ability to become pregnant through a donated egg or embryo.
In most people with Swyer syndrome, the cause is unknown. However, variants (also recognized as mutations) in one of several genes have actually been uncovered to reason the problem in some influenced individuals.
Variants in the SRY gene have actually been found in about 15 percent of individuals with Swyer syndrome. The SRY gene, situated on the Y chromosome, provides instructions because that making the sex-determining region Y protein. This protein is a transcription factor, which means it attaches (binds) to details regions the DNA and helps control the activity of particular genes. The sex-determining region Y protein starts procedures that are affiliated in male-typical sex development. These processes reason a fetus to build male gonads (testes) and prevent the development of female reproductive structures (uterus and fallopian tubes). SRY gene variants that reason Swyer syndrome avoid production the the sex-determining an ar Y protein or an outcome in the manufacturing of a nonfunctioning protein. Without sensible sex-determining region Y protein, a fetus will not construct testes but will construct a uterus and fallopian tubes, in spite of having an X and a Y chromosome.
Swyer syndrome can also be led to by variants in the MAP3K1 gene; research indicates that variants in this gene may account for approximately 18 percent the cases. The MAP3K1 gene provides instructions because that making a protein that helps manage signaling pathways that regulate various procedures in the body, consisting of processes of identify sex characteristics before birth. The variants in the MAP3K1 gene that reason Swyer syndrome diminish signaling that leads come male-typical sex development and enhance signaling that leads to female-typical sex development. These alters in signaling protect against the development of testes and permit the advance of a uterus and also fallopian tubes.
Variants in the DHH and NR5A1 genes have likewise been figured out in a little percentage of human being with Swyer syndrome. The DHH gene offers instructions because that making a protein the is necessary for early development of organization in many parts of the body. The NR5A1 gene gives instructions for producing an additional transcription factor dubbed the steroidogenic element 1 (SF1). This protein helps regulate the task of several genes pertained to sex breakthrough and the manufacturing of sex hormones. Variants in the DHH and NR5A1 gene disrupt the procedure of sex development, preventing affected individuals v a 46,XY karyotype from arising testes and also causing them to build a uterus and fallopian tubes.
Changes affecting other genes have also been established in a few people v Swyer syndrome. Nongenetic factors, such together hormonal drugs taken by the mother during pregnancy, have very rarely been associated with this condition.
Learn an ext about the genes linked with Swyer syndrome
Additional details from NCBI Gene:
Most cases of Swyer syndrome space not inherited; they happen in people with no background of the condition in their family. These instances often result from brand-new (de novo) variants in a gene the occur during the development of reproductive cell (eggs or sperm) or in early embryonic development. Noninherited cases can also result from nongenetic causes.
SRY-related Swyer syndrome is usually caused by a new variant. However, some people with Swyer syndrome inherit an changed SRY gene native an unaffected father who is mosaic because that the variant. Mosaic way that an individual has the variant in some cells (which can encompass some reproductive cells) but not in others. In rarely cases, a dad may lug the different in every cell of the body but additionally has other genetic variations that prevent him native being affected by the condition. Because the SRY gene is on the Y chromosome, Swyer syndrome caused by SRY gene variants is defined as having a Y-linked inheritance pattern.
When Swyer syndrome is linked with an MAP3K1 or NR5A1 gene variant, the problem is additionally usually caused by a new variant. In the rarely inherited cases, the variant might be inherited from either parent, since these genes space not top top the Y chromosome. In these cases, the problem has one autosomal dominant pattern that inheritance, which way one copy of the changed gene in each cell is adequate to cause the condition. However, the parent v the hereditary variant typically does not have signs and also symptoms.
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Swyer syndrome caused by variants in the DHH gene is inherited in an autosomal recessive pattern, which method both duplicates of the gene in each cell have actually variants. The parental of one individual v an autosomal recessive condition each have one copy that the transformed gene. Females v one DHH gene variant normally have usual sex development. Males through one DHH gene variant may additionally be unaffected, or lock may have actually genital distinctions such together the urethra opened on the underside of the penis (hypospadias).