How and why genes are regulated. Every somatic cell in an organism contains identical genetic instructions. They all share the same genome. What makes them different? In cellular differentiation, cells become specialized in structure and function. Certain genes are turned on and off in the process of gene regulation.
Patterns of gene expression in differentiated cells. In gene expression, a gene is turned on and transcribed into RNA. The information flows from genes to proteins, genotype to phenotype. The information flows from DNA to RNA to proteins. The great differences among cells in an organism must result from the selective expression of genes.
The regulation of genes in bacteria; Natural selection has favored bacteria that express only certain genes. It is also, at specific times when the products are needed by the cell. So how do bacteria selectively turn their genes on and off?. An operon includes, a cluster of genes with related functions. It also includes, the control sequences that turn the genes on or off. The bacterium E.coli used the lac operon to coordinate the expression of genes that produce enzymes used to break down lactose in the bacterium’s environment.
There are three things the lac operon uses. A promoter, a control sequence where the transcription enzyme initiates transcription. An operator, a DNA segment that acts as a switch that is turned on or off. A repressor, which binds to the operator and physically blocks the attachment of RNA polymerase.
Gene regulation in Eukaryotic Cells. Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be regulated.
The regulation of DNA packing. Cells may use DNA packing for long-term inactivation of genes. X chromosome inactivation occurs in female mammals. It is also when one of the two X chromosomes in each...