| 11. | Of these, Sir2p, Sir3p and Sir4p form the core of heterochromatin.
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| 12. | Also in yeast, RNA silencing has been shown to maintain heterochromatin structure.
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| 13. | Constitutive heterochromatin can affect the genes near itself ( position-effect variegation ).
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| 14. | The constitutive heterochromatin stains darker because of the highly condensed nature of the DNA.
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| 15. | Histone modifications are one of the main ways that the cell condenses constitutive heterochromatin.
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| 16. | Sir3p binding follows, further condensing the heterochromatin.
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| 17. | PRC2 recruits MACROH2A is a replacement for histone H2A that also supports heterochromatin formation.
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| 18. | Reasons might be the presence of repetitive sequences, extensive DNA methylation, or heterochromatin.
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| 19. | This heterochromatin greatly reduces, if not completely silences gene expression of the Barr body.
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| 20. | Yeast, " Drosophila " and mammals all have heterochromatin flanking their centromeres.
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