Definition of Facultative heterochromatin
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.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 6/14/2012