Chromatin

Chromatin is the genetic makeup of chromosomes, consisting of DNA and proteins.

In 2369, Julian Bashir and Jadzia Dax noticed that the chromatin pattern of a subject they were studying was changing, making them realise that the subject was becoming humanoid. 

Bashir and, a crewmember of the USS Aldebaran (Nebula class), spent several years corresponding on chromatin formation.