MCB164+S08+ICE+7+key

MCB164+S08+ICE+7+key - D. Demethylation of cytosine is...

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MCB164 S08, In class exercise #7 May 27, 2008 In Arabidopsis, a gene containing both a chromodomain and a cytosine methyltransferase domain (called “chromomethyltransferase” or CMT) has been identified. These combined functions are important for the establishment of DNA methylation. Recall, the chromodomain binds to nucleosomes containing H3K9 2me . 1. (3 points) Based on this information, predict a mechanism of CMT-mediated gene silencing in plants: (circle one answer) A. Cytosine methylation is required for H3 methylation. B. H3 methylation at position K9 promotes methylation of nearby cytosines. C. Demethylation of H3K9 2me is required for cytosine methylation.
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Unformatted text preview: D. Demethylation of cytosine is required for H3 methylation at K9. E. Demethylation of H3K9 2me is required for cytosine demethylation. 2. (3 points) Cytosine methylation is associated with (active / inactive ) chromatin. (circle one) 3. (4 points) Would you predict that CMT is directly involved in the spreading of heterochromatin into adjacent euchromatin? Explain your answer No: CMT recognizes a different mark than it promotes. That means that there is not a mechanism to propagate the mark by spreading as HP-1 does. HP-1 both recognizes H3K9 2me and recruits a methylase that creates another binding site for HP-1....
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