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 Heterochromatin, facultative
Medically reviewed by Dr. Otari Nergadze, Neurosurgeon | Updated: January 2026
Heterochromatin, facultative: Heterochromatin that need not always be heterochromatic but which has the faculty to return to the normal euchromatic state. The inactive X chromosome is made up of facultative heterochromatin. When a woman transmits that X to a son, it reverts to euchromatin and genetic activity.
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