Complete the account of chromatin states.
Loosely packed chromatin is called ______ and is actively transcribed, while densely packed chromatin is called ______ and is largely ______. A cell can regulate its genes by moving regions between these two states, which means the packing must be ______.
Word bank: euchromatin · heterochromatin · silenced · reversible · permanent
Hints
- The two states differ in both density and activity.
- If packing were permanent, gene regulation by this route would be impossible.
Show the answer
Loosely packed chromatin is called euchromatin and is actively transcribed, while densely packed chromatin is called heterochromatin and is largely silenced. A cell can regulate its genes by moving regions between these two states, which means the packing must be reversible.
Reversibility is the essential point: packing is a regulatory mechanism, not just storage. A gene silenced by condensation can be reactivated by decondensing the region, and much of development works this way.
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