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Eukaryotic Gene Expression

Eukaryotic Gene Expression. Why is gene regulation more complex in eukaryotes than prokaryotes? Eukaryotes have larger more complex genome Eukaryotic DNA must be more highly organized than prokaryotic DNA. Prokaryotic DNA circular smaller than eukaryotic DNA

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Eukaryotic Gene Expression

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  1. Eukaryotic Gene Expression • Why is gene regulation more complex in eukaryotes than prokaryotes? • Eukaryotes have larger more complex genome • Eukaryotic DNA must be more highly organized than prokaryotic DNA

  2. Prokaryotic DNA circular smaller than eukaryotic DNA associated with very few proteins less structured and folded Eukaryotic DNA associated with lots of histone proteins to form chromatin fiber very extended and tangled during interphase condensed into discrete chromosomes during mitosis Prokaryotic vs. Eukaryotic DNA

  3. Eukaryotic Development • Cellular differentiation is the specialization of cells during development • Since all cells have the same DNA, how can differentiation occur? • Gene regulation.

  4. Selective Gene Expression • How do cells become specialized? • Different genes are activated at different times during development. • Each cell utilizes only about 3% of genome

  5. DNA PackingHelps regulate gene expression • DNA in one human cell’s 46 chromosomes would be 3 meters long. • How, then, does it all fit into the nucleus? • DNA packing • Why do densely packed regions of chromosomes inactivate gene expression? • RNA pol can’t get to the gene for transcription.

  6. What is the difference between heterochromatin and euchromatin? • Heterochromatin remains highly condensed even during interphase • Barr bodies are X chromosomes condensed into heterochromatin • Telomeres, centromeres also heterochromatin • euchromatin is chromatin that is not condensed and can be transcribed

  7. Control of Gene Expression • What are the steps from chromosome to functional protein? • Unpacking Transcription mRNA processing  export from the nucleus  translation  protein modification • ANY of these steps can be regulated in eukaryotes

  8. Control of Gene Expression

  9. Chromatin modification • DNA methylation; the addition of methyl groups to DNA • essential for inactivation of the DNA • Inactive genes in a cell are methylated • Epigenetic memory due to methylating enzymes that methylate the new daughter strand the same as the parent strand. • Can be passed on in repro • Histone acetylation is the attachment of an acetyl group to histone proteins • acetylation increases likelihood for transcription of the DNA

  10. Transcriptional Control • Transcription factors allow RNA pol to find the promoter region • association between transcriptional factors and enhancer or promoter region regulates gene expression

  11. Posttranscriptional control • Regulation of RNA processing • Regulation of mRNA degradation • Can last from hours to weeks • Regulation of translation • initiation sequence can be blocked

  12. Protein Degradation;posttranslational control

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