1.  Introduction to the X Chromosome:

  • Humans and many other organisms have two sex chromosomes, one of which is X.
  • Females have two X chromosomes (XX), and males have one X and one Y (XY).

- The presence or absence of the Y chromosome determines the biological sex.

2.  Genes and Functions of X Chromosome:

  • The X chromosome contains approximately 800 genes involved in diverse biological
  • The malfunction or loss of these genes can result in X-linked genetic diseases, diseases influenced by X-chromosome inactivation (XCI) escape and diseases tied to X-chromosome

3.  X-linked Genetic Diseases:

  • Diseases from mutations in genes on the X chromosome are termed X-linked genetic
  • Males are more prone to these diseases as they possess only one X chromosome.
  • Examples include red-green colour blindness, Duchenne muscular dystrophy, and

4.  X Chromosome Aneuploidies:

  • Aneuploidies, abnormalities in the number of chromosomes in a cell, can result in diseases when they occur in the X chromosome.
  • Examples include Klinefelter syndrome (with an additional X chromosome) and Turner syndrome (with one less X chromosome).

5.  Understanding

  • Chromosome Inactivation (XCI) Escape:
  • One X chromosome is typically inactivated in females to maintain a gene balance. Problems arise when inactivation is incomplete or skewed.
  • These issues can contribute to X-linked disorders, certain cancers, and autoimmune
  • Two non-coding RNAs, Xist and Tsix, discovered in the 1990s, are crucial in regulating the XCI process.

6.  Linking X Chromosome and Autoimmune Diseases:

  • Recent studies indicate a relationship between gene changes on the X chromosome and autoimmune diseases.
  • Autoimmune conditions — where the immune system attacks healthy cells — are more prevalent in females than males.
  • A study found that manipulating the gene Xist led to lupus-like symptoms by reactivating other inactive genes on the X chromosome.

7.  Correlation Between X Chromosome and Alzheimer's Disease:

 Alzheimer's disease, more common in women than men, might be related to the X chromosome.

  • A gene on the X chromosome, USP11, escapes inactivation and is overexpressed in
  • This overexpression results in tau protein accumulation, which can lead to Alzheimer's

Study of the X chromosome has uncovered its pivotal role in auto-immune diseases and Alzheimer’s disease. Hence, the understanding and research of the X chromosome is crucial not only for genetics but also for medical science. This could potentially lead to the development of new treatments and prevention methods for such diseases.