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The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child.
Trisomy X, also known as triple X syndrome and characterized by the karyotype [note 1] 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it.
Location of the FMR1 gene on the X chromosome. Fragile X syndrome is a genetic disorder which occurs as a result of a mutation of the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the X chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5' untranslated region of FMR1.
X-linked recessive inheritance. X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation (see zygosity).
Males with Klinefelter syndrome typically have one extra copy of the X chromosome in each cell, for a total of two X chromosomes and one Y chromosome (47,XXY). It is less common for affected males to have two or three extra X chromosomes (48,XXXY or 49,XXXXY) or extra copies of both the X and Y chromosomes (48,XXYY) in each cell.
[citation needed] An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called "trisomy 21". [7] An example of monosomy in humans is Turner syndrome, where the individual is born with only one sex chromosome, an X. [8]
X-linked alpha thalassemia mental retardation syndrome (ATR-X) X-linked dominance; X-linked ichthyosis; X-linked juvenile retinoschisis; X-linked lymphoproliferative syndrome; X-linked mental retardation; X-linked mental retardation and macroorchidism; X-linked mental retardation associated with marXq2; X-linked mental retardation Brooks type
Sons have an equal chance of receiving either of their mother's X chromosomes. In such a case, where both parents carry and thus are affected by an X-linked dominant disorder, the chance of a daughter receiving two copies of the X chromosome with the defective gene is 50%, since daughters receive one copy of the X chromosome from both parents.