Honors Genetics Special Topics: Epigenetics – Flashcards
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What are the major mechanisms of epigenetic genome modification?
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DNA methylation; long noncoding RNAs binding to chromatin-modifying enzymes; binding of RISC to target mRNA molecules; histone modification involving acetyl, methyl, and phosphate groups; chromatin remodeling
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What parts of the genome are reversibly methylated?
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CpG-rich regions and Promoter sequences. When a gene is imprinted by methylation, it remains transcriptionally silent.
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How are reversible chemical changes to histones linked to chromatin modification?
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Reversible histone modifications influence the structure of chromatin by altering the accessibility of nucleosomes to the transcriptional machinery.
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What is the difference between silencing genes by imprinting and silencing by epigenetic modifications?
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Imprinted alleles are transcriptionally silent in all cells of the organism, whereas epigenetic modifications can be reactivated by environmental signals.
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How do microRNAs regulate epigenetic mechanisms during development?
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MicroRNA is a part of RITS complexes, which reversibly convert euchromatic chromosome regions into facultative heterochromatin, silencing the genes located within these newly created heterochromatic regions. MicroRNA is a part of RISCs, which act as repressors of gene expression by binding to and destroying target mRNA molecules carrying sequences complementary to the RISC microRNA.
