Hétérochromatine

The hétérochromatine corresponds to Chromatine with the state condensed, made of fibers B from 200 to 300 Angström of diameter. The hétérochromatine (or more precisely its Histone S) is schematically hypoacétylée and hyperméthylée compared to the Euchromatine. The hétérochromatine is localized mainly in periphery of the core and the nucleole (whereas the euchromatine is distributed inside the nucleoplasme).

The hétérochromatine is the started from inactive chromatin on the level transcriptionnel .

One distinguishes:

the constitutive hétérochromatine , corresponding to apparently inactive portions of Chromosome S in all the cells and carrying repetitive sequences, of which the greatest parts are near the centromères and télomères

;

the optional hétérochromatine , corresponding to variable portions of the hétérochromatine. According to the type of cell, such or such portion is condensed, and of this fact inactivated. In the same way for the same cell, the same portion of hétérochromatine can be condensed or not, depending on the state of differentiation of this one.

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