Control of Gene Expression

Control of Gene Expression - Control of Gene Expression I....

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Control of Gene Expression I. Mechanisms of regulating gene expressions: a. At the initiation of transcription (currently seems to be the most important mechanism): i. Affecting if the RNA polymerase binds to the promoter or not b. Processing of the primary messenger RNA transcript i. Can be spliced together in different ways c. Transport of the mRNA out of the nucleus (through nuclear pores): i. Only roughly 50% of mRNA leaves the nucleus ii. Is it selective? d. Half-life of mRNA: i. Prokaryote mRNA lasts on average 3 minutes ii. In Eukaryotes, the messages last from minutes to hours e. Small RNA’s: i. Micro-RNA’s (miRNA) 1. Tend to bind or cleave messages ii. Small-Interfering RNA’s (siRNA) 1. Degrade messages f. Protein Synthesis (translation): i. Affecting initiation (determining whether or not it starts) g. Post-translational control: i. Control of the actual protein that is produced h. Fig. 16.20 II. Why regulate gene expression? a. Efficiency: it would be a mess if cells were to make all proteins all the time, and it would cost too much energy b. Prokaryotes:
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i. The genes that are turned on depend on their environment ii. The food that’s around affects which genes are turned on and off c. Eukaryotes: i. Homeostasis: genes are turned on and off in order to maintain internal conditions ii. Developmental issues iii. Apoptosis III. Transcriptional Regulation a. RNA polymerase needs to bind to DNA to transcribe it. This binding is what is regulated i. Regulatory sequence 1. Regulates the coding of genes, typically ahead of coding region (closer to 5’
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Control of Gene Expression - Control of Gene Expression I....

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