Control of Gene Expression How are genes turned on and off in eukaryotic cells? Important Overview of differential gene expression fig. 18.6 here What are different ways by which specific genes can be turned on or off in specific eukaryotic cells ? 1. DNA packing (euchromatin & heterochromatin), histones and nucleosomes, histone acetylation, DNA methylation, 2. beginning transcription (the most important specific control)-transcription factors (proteins) bind to promoter (DNA) and to each other so RNA polymerase can bind; TF’s required in eukaryotes -activator proteins bind to enhancer DNA to increase transcription; repressor proteins decrease initiation of transcription 3. mRNA splicing (alternate splicing in different cells produces slightly different mRNA's for translation) 4. mRNA enzymatic breakdown (how long does mRNA last?) 5. initiation of translation (mRNA activation) 6. protein processing (chemical modification, sugar chains, phosphorylation, disulfide bridges, quaternary structure)
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