Chromatide
A chromatide is a molecule of DNA (nucléofilament) associated with proteins Histones and proteins not histones (PNH). A chromatide with the shape of a stick which can have various degrees of condensation according to the moments of the cellular cycle or the activity of transcription of the Gènes.
This structural unit appears as a Chromosome only during the cellular divisions (Mitose or Méïose). The remainder of time, the whole of the chromatides form the Chromatin.
Each chromosome of a cell can be made up of one or two chromatides depending on its state:
- just after a mitosis, or the second meiotic division, each chromosome is made up only of a chromatide,
- the remainder of time, after duplication of the DNA, each chromosome consists of two chromatides completely identical, connected by the Centromère, thus giving to the two sticks the shape of X.
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