 | Androgen insensitivity syndrome: Encyclopedia II - Androgen insensitivity syndrome - Genetics inheritance and incidence
Androgen insensitivity syndrome - Genetics inheritance and incidence
The gene, AR, for the human androgen receptor is located within the Xq11-12 area of the X chromosome. Effects of the AIS mutations behave as sex-linked recessive traits, causing minimal or no effects in 46,XX women. In other words, since 46,XX women have two X chromosomes, and hence two copies of the gene for the androgen receptor, no problems occur if one of the genes is defective. Since a 46,XY person has only a single X chromosome, a deleterious mutation of the androgen receptor gene on the only X chromosome can cause any of several forms of androgen insensitivity syndrome.
A 46,XX woman who has one mutated AR gene is a "carrier" of AIS and may pass androgen insensitivity on to her children. As in some other X-linked recessive conditions, carrier mothers may display some minor traits of the condition. AIS carriers often have reduced axillary and pubic hair and a reduction in normal adolescent acne.
Except in the rare instance of a new mutation, a 46,XY person affected with AIS has inherited his/her single X chromosome with the defective gene from his/her mother, who may have an affected sibling. Generally the condition caused by a familial mutation will affect family members similarly, though differing degrees of severity occasionally occur in different relatives with apparently the same mutation. Carrier testing is now available for relatives at risk when a diagnosis of AIS is made in a family member.
Over 100 AR mutations causing various forms of AIS have been reported. In general, the milder types of AIS (4 and 5 in the list below) are caused by simple missense mutations with single codon/single amino acid difference, while CAIS and the nearly complete forms result from mutations that more severely affect the shape and structure of the protein. About one third of cases of AIS are new mutations rather than familial. A single case of CAIS attributed to an abnormality of the AF-1 coactivator (rather than AR itself) has been reported (OMIM 300274).
Incidence of complete AIS is about in 1 in 20,000. The incidence of milder degrees may be lower but is not well established because of greater ascertainment uncertainty.
Other related archives46, XX, 46, XY, AMH, Acne, DNA, FSH, Gender identity, Johns Hopkins Hospital, Kennedy disease, LH, Puberty, SRY, Sexual differentiation, Testosterone, X chromosome, X-linked recessive, XY, abdomen, acne, adrenals, ambiguous, amenorrhea, amino acid, amino acids, amniocentesis, androgen, androgen receptor, anti-müllerian hormone, appendectomy, appendicitis, azoospermia, body odor, bone, breast, button, cell, cervix, chromatin, clitoris, codon, coitus, conception, cytoplasm, dihydrotestosterone, epiphyseal closure, estradiol, estrogen, fat, fertility, gender identity, genetic counselor, genital, gynecomastia, hernia, hypospadias, hypothalamus, infertility, inguinal canals, inguinal hernia, intersex, karyotype, labia, menarche, menses, missense mutations, mutations, müllerian ducts, nucleus, ovaries, pathophysiology, penis, perineum, phallus, phenotypes, phosphorylated, pituitary, primary sex characteristics, progesterone, promoter, prostate, protein, pubertal, puberty, pubic hair, receptor, recessive, scrotum, secondary sex characteristics, seminal vesicles, sex hormone binding globulin, sexual differentiation, sexual intercourse, sideburn, sperm, spermatogenesis, steroid, surgical corrections, testes, testosterone, transcription, ultrasound, unaffected carrier, undervirilization, urethral, uterus, vagina, vaginas, vas deferens, wolffian, zinc finger
 Adapted from the Wikipedia article "Genetics inheritance and incidence", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki |
