In addition, enzymes add methyl groups to the DNA of the inactive X, resulting in repression of transcription. The inactivated X is visible during interphase in mitosis as a condensed chromosome, called a Barr body. It replicates in the S (synthesis) phase of the cell cycle later than does the active copy. Inactivation of one of the two X copies in a female leaves only one active. X chromosome in any cell. An individual who has three X chromosomes has two inactivated copies of the X, producing two Barr bodies.