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Control of Gene Expression

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Presentation on theme: "Control of Gene Expression"— Presentation transcript:

1 Control of Gene Expression
Chapter 16 Genes and Development

2 Proteins can determine the DNA sequence by binding the major groove of DNA.
Proteins binding the minor groove cannot determine the exact sequence of bases.



5 Prokaryotic gene regulation
Lac Operon



8 Prokaryotic gene regulation
Trp Operon Biosynthesis of the amino acid typtophan Therefore, the regulation is the opposite of the lac operon.


10 Eukaryotic gene regulation


12 Enhancer (DNA sequence)
Looping Activator (protein)




16 Pi ATP ADP + ATP -dependent remodeling factor 1. Nucleosome sliding
2. Remodeled nucleosome 3. Nucleosome displacement 4. Histone replacement


18 RNA Polymerase II RNA Polymerase II microRNA gene microRNA gene Pri-microRNA Pri-microRNA Nucleus Nucleus Drosha Pre-microRNA Pre-microRNA Drosha Exportin 5 Exportin 5 Cytoplasm Dicer Mature miRNA RISC mRNA RISC mRNA cleavage mRNA RISC RISC Inhibition of translation

19 Exogenous dsRNA, transposon, virus
Repeated cutting by dicer P P P P P siRNAs P P P siRNA in RISC Ago + Ago RISC RISC mRNA Cleavage of target mRNA


21 Primary RNA transcript Mature RNA transcipt
RNA polymerase II 1. Initiation of transcription Most control of gene expression is achieved by regulating the frequency of transcription initiation. Cut intron 2. RNA splicing Gene expression can be controlled by altering the rate of splicing in eukaryotes. Alternative splicing can produce multiple mRNAs from one gene. DNA 3´ poly-A tail 5´ cap Primary RNA transcript Exons Introns Mature RNA transcipt

22 3. Passage through the nuclear membrane Gene expression
Large subunit 3. Passage through the nuclear membrane Gene expression can be regulated by controlling access to or efficiency of transport channels. 3´ poly-A tail Nuclear pore mRNA 5´ cap Small subunit 4. Protein synthesis Many proteins take part in the translation process, and regulation of the availability of any of them alters the rate of gene expression by speeding or slowing protein synthesis.

23 Completed polypeptide chain 6. Posttranslational modification Phosphorylation or other chemical modifications can alter the activity of a protein after it is produced. 5. RNA interference Gene expression is regulated by small RNAs. Protein complexes containing siRNA and miRNA target specific mRNAs for destruction or inhibit their translation. P RISC P




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