Skewed X inactivation in X-linked disorders

Semin Reprod Med. 2001 Jun;19(2):183-91. doi: 10.1055/s-2001-15398.


X chromosome inactivation is a process by which the dosage of proteins transcribed from genes on the X chromosome is equalized between males (XY) and females (XX) through the silencing of most genes on one of the two X chromosomes in females. Although the choice of which of the two X's is inactivated is entirely random, not all women have a 50:50 ratio of cells with one or the other X chromosomes active. A number of different mechanisms lead to extremely skewed ratios and this can result in expression of the phenotype of X-linked recessive disorders in females. Nonrandom X inactivation patterns are also associated with selective female survival in male-lethal X-linked dominant disorders or with variable severity of the phenotype in women carrying X-linked dominant mutations. These features are important for the study and gene identification of X-linked disorders and for counseling of affected families.

Publication types

  • Review

MeSH terms

  • Diseases in Twins / genetics
  • Dosage Compensation, Genetic*
  • Female
  • Gene Dosage
  • Genes, Dominant / genetics
  • Genes, Lethal / genetics
  • Genetic Linkage / genetics*
  • Humans
  • Male
  • Mosaicism / genetics
  • Mutation / genetics
  • Selection, Genetic
  • Sex Chromosome Aberrations*
  • Skin / metabolism
  • Stochastic Processes
  • X Chromosome / genetics*