X Chromosome

Introduction

Human X chromosome

This section of notes introduces the X chromosome and its role in development. There is a separate page discussing X chromosome inactivation that occurs in female development to provide the correct gene dosage.

X Chromosome Overview

• 1400+ genes
• 150 million base pairs
• Contains about 5% of the haploid genome.
• Genes encode house-keeping and specialized functions.
• Conserved in gene content between species.
• In females, one of the X-chromosomes is inactivated in each and every cell (known since 1961).
  • This inactivation occurs during embryogenesis.
  • X Inactivation appears to be random in somatic cells. (mosaic pattern)
  • The process starts at the "X inactivation centre" and spreads along the chromosome.

References

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