# Gene Regulation --- **Gene regulation** describes how organisms can chose which of it's many [[gene|genes]] to [[gene expression|express]]. Each organism must employ its genetic information carefully. In humans, every cell in our bodies has basically the same DNA, but each cell needs to selectively turn on the proper genes at the proper times. All cells regulate their genes depending on their environment—be it the surrounding cells in the same organism, or the available nutrients in the surrounding environment for prokaryotes. ## Transcriptional Control **Transcriptional control** is when regulatory proteins stop [[RNA polymerase]] from binding to the promoter and initiating [[transcription]]. This is the most efficient form of gene regulation. Making proteins is *expensive*, not only in materials but also time and energy. Bacteria are especially optimized for conserving resources, and do not turn on genes unless they really need to. ## Translational Control **Translational control** is when the mRNA is created, but prevented from [[translation|translating]] to proteins (either my affecting it's life span or it's ability to be translated). Allows a more rapid change than transcriptional control. ## Post-Translational Control **Post-translational control** is when the protein is translated, but prevented from properly undergoing post-translational modification, we have "post-translational control". Is the most rapid form of gene regulation. There is a trade-off between speed and conservation of resources and energy. ### Post-Translational Modification **Post-translational modification** takes place after [[translation#Post-Translational Modification|translation]] is terminated. Freshly-minted proteins are not quite yet fully formed, and need these modifications to fully function, such as being properly [[protein folding|folded]]. Something else that happens is having other things added to the proteins, like [[carbohydrates|sugars]], [[lipids]] or [[phosphorylation|phosphates]]...I'm sure this is important but I'm not going to worry about that too much. ## Transcription Factors **Regulatory transcription factors** are [[protein|proteins]] that bind to the DNA at specific sites in order to turn different [[gene|genes]] them on or off. ## Positive and Negative Control ### Positive Control **Positive control** is when a regulatory transcription factor called an *activator* binds to DNA and triggers transcription. Since the default state in [[eukaryote|eukaryotes]] is to have their genes wrapped up in the dense, protective [[chromatin]], there needs to be some sort of activation before the gene can be [[transcription|transcribed]]. For an example, see the positive regulation of the [[lac operon#Positive Regulation|lac operon]]. ### Negative Control **Negative control** is when a regulatory transcription factor called a "repressor" binds to the [[transcription|promoter]] region of [[DNA]] and blocks transcription. Genes that are transcribed all the time, or without regulation are said to be transcribed "constitutively", and [[mutation|mutants]] that have runaway translation are called "constitutive mutants". For an example, see the negative regulation of the [[lac operon#Negative Regulation|lac operon]]. ## RNA Interference **RNA interference** controls the expression of [[RNA]] ## Global Gene Regulation **Global gene regulation** is the coordinated regulation of many genes. A group of genes and operons that contain the same regulatory sequence and are controlled by a single type of regulatory protein are called a "regulon". ___