Long noncoding RNA X-chromosome
inactive specific transcript
In the nematode Caenorhabditis elegans, sex determination is a direct function of X-chromosome
dosage, with XX being hermaphrodites if the ratio of X-chromosomes
to autosomes (A) is balanced (2X/2A = 1), and X0 being male (Hodgkin 2002).
When breed-specific X-chromosome
regional gene expression differences were determined, the chromosomal band Xq13, which contains 13 genes including OGT and X inactivation-specific transcript (XIST), ranked highest by criteria of placental gene expression and chromosomal location .
Sex chromatin seen as darkly staining mass at the nucleus of all non-dividing cells of genotypically females represents the heterochromatin of the inactivated X-chromosome
Although X monosomy is the most frequent chromosomal finding, in some patients with the Turner syndrome the karyotype shows variants of X-chromosome
abnormalities such as deletions, duplications, inversions, X/autosomal balanced translocations, and rings.
The selection of which X-chromosome
(derived from the mother or the father) is inactivated appears to be random but that selection is maintained through subsequent cell divisions.
revealed myelolipomas and displayed X-chromosome
inactivation in both fat and haematopoietic elements, which suggests clonal origin of myelolipoma.
The best example is Rett syndrome which was diagnosed as a pervasive developmental disorder in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV)  but re-classified as a neurological disorder in the more recent fifth edition of the diagnostic manual (DSM-5)  because research found it was caused by a single X-chromosome
mutation in the methyl-CpG-binding protein 2 (MEC([p.
A striking example of such developmentally regulated gene control is X-chromosome
inactivation (XCI), whereby one of the two X chromosomes in females is silenced during embryogenesis.
X chromosome aneuploidy: 45 XO or variant of X-chromosome
Several causes such as skewed X-chromosome
inactivation, genomic imprinting, single gene mutations, chromosomal instability and sperm chromosomal abnormalities have been suggested to explain the reproductive losses (13).
inactivation of the human TIMP1 gene.