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13 Cards in this Set
- Front
- Back
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which is the centromere-specific histone |
H3 variant |
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what types or chromatin structure does centromeres have |
heterochromatin |
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why is access to DNA required |
1. DNA metabolism 2. DNA repair 3. replication 4. transcription |
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what is chromatin remodelling |
energy-dependent displacement or reorganisation of nucleosomes in conjunction with activation of genes for transcription |
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what happens in lysine acetylation |
lysine acetylation in histone tails results in loss of positive charge and a reduction in binding to DNA---so chromatin opens up---increased access to DNA |
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what are the 2 histone modification enzymes used in lysine acetylation/deacetylation |
1. HAT/KAT - Histone acetyltransferase/ lysine acetyltransferase 2. HDAC - Histone deacetylase |
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what do HAT and HDAC do |
HAT - transcription activation HDAC - repressor of transcription |
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what are the 2 enzymes used in lysine methylation/demethylation |
1. KMT - Histone methyltransferases 2. KDM - Histone demethyltransferases |
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what happens in DNA methylation |
covalent addition of methyl groups on 5th position of cytosine within self-complimentary CpG dinucleotides |
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which are the highly methylated sequences |
1. satellite DNA 2. repetitive elements (transposons) 3. exons of genes |
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what are CpG islands |
unmethylated DNA sequences, found at the start of transcription |
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what does DNA methylation do to DNA |
compacts chromatin and is associated with transcriptional repression |
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are modification reversible or irreversible |
reversible |
