X Chromosome
From Embryology
Introduction
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.
