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genetics chapter 18
Gene expression in Prokaryotes
| Question | Answer |
|---|---|
| what is Rho dependent termination? | a protein factor called Rho, a helicase enzyme that unwinds the mRNA from the DNA template, helps dissociate RNA polymerase from the template. |
| what is Rho independent termination? | a sequence of bases in the RNA forms a secondary structure, known as a hairpin loop, that signals the release of RNA polymerase from the completed RNA. |
| does Rho independent or dependent termination involve hairpin loop formation? | rho independent formation |
| what is polycistronic mRNA? | single mRNA molecule that contains multiple coding sequences (cistrons), each of which can be translated into a different protein. |
| how are anabolic and catabolic pathways regulated differently? | catabolic pathways are tuned on only when the complex molecules to be broken down are present in the cell’s environment. anabolic pathways are repressed should be turned on only when the cell does not have enough of the needed end product |
| what is a helix-turn-helix motifs in proteins? what is it used for? | two alpha helical regions that are separated by a turn; it fits into the major groove of the DNA. |
| what genes are found in the Lac operon? | lacZ, lacY, and lacA |
| what is an operator? | DNA regulatory sequences found in prokaryotic operons that serve as the binding site for repressor proteins |
| how do repressors and inducers work here? | Repressors and inducers regulate gene expression by controlling whether a repressor can bind to the operator. a repressor binds to the operator and the inducer binds to the repressor |
| what is allolactose and what role does it play? | a derivative of lactose and is a natural inducer of the lac operon; it binds to the lac repressor (LacI). The binding changes the repressor’s shape so it cannot bind the operator.the lac operon is turned on, allowing transcription of lacZ, lacY, and lacA. |
| how does the lac operon work? | allows E. coli to use lactose as an energy source only when lactose is present and glucose is low. controls the expression of lacZ, lacY, and lacA. depending on the levels of lactose or glucose it will be turned off or go through cell signaling pathways. |
| how are the genes of the Trp operon controlled? | controlled by a repressor that becomes active only when bound to tryptophan, turning the operon OFF when tryptophan levels are high. It is regulated by attenuation, a mechanism that stops transcription early if the cell has plenty of tryptophan. |
| what role does tryptophan play in the control of the Trp operon? | Tryptophan acts as a corepressor for the trp operon. When levels are high, it binds and activates the trp repressor, which then blocks the operator and shuts off transcription. When levels is low, the repressor stays inactive, allowing the operon to stay |
| when does the repressor bind to the operator? | |
| what is meant by allostery? | |
| what is an allosteric protein? | |
| how do RNA leader devices work to control translation? | |
| how do stem loop structures work? | |
| what is a terminator? | |
| what is an antiterminator? | |
| what is an attenuator? | |
| how does translation by a ribosome in the 5' UTR help control translation of the coding sequence? | |
| what is a riboswitch? | |
| what is an expression platform? | |
| what is an aptamer? | |
| what are small RNAs? How do they work to control translation? | |
| what is anti-sense RNA? | |
| how are anti-sense RNA made? How do they work? |
Created by:
angievelasco