Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of Facultative heterochromatin
Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026
Facultative heterochromatin: Chromosome material that can be either heterochromatin or euchromatin.
The inactive X chromosome is made up of facultative heterochromatin. When a woman transmits that X chromosome to a son, the chromosome reverts to the euchromatic state and to genetic activity.
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