Chapter 7 Control of Gene Expression Flashcards
Depends on changes in the gene expression rather than on any changes in the nucleotide sequence of the cell’s genome
Cell differentiation
The cell types in a multicellular organism become different from one another because
They synthesize and accumulate different sets of RNA and protein molecules
A cell can control the proteins it makes by (6 controls)
- Transcriptional control
- RNA processing control
- RNA transport and localization control
- Translational control
- mRNA degradation control
- Protein activity control
Controlling when and how often a given gene is transcribed
Transcriptional control
Controlling how the RNA transcript is spliced or otherwise processed
RNA processing control
Selecting which completed mRNAs in the cell nucleus are exported to the cytosol and determining where in the cytosol they are localized
RNA transport and localization control
Selecting which mRNAs in the cytoplasm are translated by ribosomes
Translational control
Selectively destabilizing certain mRNA molecules in the cytoplasm
mRNA degradation control
Selectively activating, inactivating, degrading, or compartmentalizing specific protein molecules after they have been made
Protein activity control
No question
How does a cell determine which of its thousands of genes to transcribe?
The transcription of each gene is controlled by a regulatory region of DNA relatively near the site where transcription begins
Some regulatory regions are simple and act as
Switches thrown by a single signal
Other regulatory regions are complex and resemble
Tiny microprocessors, responding to a variety of signals in order to switch their neighboring gene on or off
*Switching devices are found in all cells that are composed of two types of fundamental components
- Short stretches of DNA of defined sequence
2. gene regulatory proteins that recognize and bind to this DNA
Regulator encoded by a bacterial virus
Lambda repressor
Shuts off the viral genes enables the viral genome to remain a silent passenger in the bacterial chromosome
Lambda repressor
No question
*Turns off the production of the proteins responsible for lactose metabolism when this sugar is absent from the medium
Lac repressor
The expression of many genes is regulated by
The available food in the environment
Manufacture the amino acid tryptophan
Five E. coli genes that code for enzymes