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The phosphorylation of Rb by CDK4/6 and CDK2 dissociates the Rb-repressor complex and serves as an on/off switch for the cell cycle. Once Rb is phosphorylated, the inhibition is released on the E2F transcriptional activity. This allows for the transcription of S phase genes encoding for proteins that amplify the G1 to S phase switch.
Genetic regulatory circuits (also referred to as transcriptional regulatory circuits) is a concept that evolved from the Operon Model discovered by François Jacob and Jacques Monod. [ 1 ] [ 2 ] [ 3 ] They are functional clusters of genes that impact each other's expression through inducible transcription factors and cis-regulatory elements .
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein).A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression.
The first natural gene circuit studied in detail was the lac operon.In studies of diauxic growth of E. coli on two-sugar media, Jacques Monod and Francois Jacob discovered that E.coli preferentially consumes the more easily processed glucose before switching to lactose metabolism.
Gene regulation works using operators and repressors in bacteria. Gene Regulation can be summarized by the response of the respective system: Inducible systems - An inducible system is off unless there is the presence of some molecule (called an inducer) that allows for gene expression. The molecule is said to "induce expression".
Structure of a gene regulatory network Control process of a gene regulatory network. A gene (or genetic) regulatory network (GRN) is a collection of molecular regulators that interact with each other and with other substances in the cell to govern the gene expression levels of mRNA and proteins which, in turn, determine the function of the cell.
The two most commonly used inducible expression systems for research of eukaryote cell biology are named Tet-Off and Tet-On. [3] The Tet-Off system for controlling expression of genes of interest in mammalian cells was developed by Professors Hermann Bujard [] and Manfred Gossen at the University of Heidelberg and first published in 1992.
Enhancers function as a "turn on" switch in gene expression and will activate the promoter region of a particular gene while silencers act as the "turn off" switch. Though these two regulatory elements work against each other, both sequence types affect the promoter region in very similar ways. [4]