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Bis 101
Lecture 10
| Question | Answer |
|---|---|
| How are structural genes regulated? | So proteins are only produced at certain times and specific amounts |
| How are constitutive genes regulated? | They aren't, they need constant levels at all times or we would die |
| What are the benefits of gene regulation? | Conserve energy, and ensure that the correct genes are expressed in the right development stage and quantity. |
| Where does gene regulation occur in bacteria? | Most commonly at the level of transcription from DNA to RNA, it controls the rate at which mRNA is translated |
| How do transcription factors control the rate of transcription? | The bind the DNA in the vicinity of a promoter and affect the transcription of nearby genes |
| What is positive control transcription factor? | Activators, promotes transcription, has its own binding site |
| What is negative control transcription factor? | Repressors, represses transcription, acts on operator |
| What is an allosteric effector molecule? | A molecule that binds to a regulatory transcription factor and causes conformational change effecting whether it can bind to the DNA or not. |
| What are the two domains or sites that on the regulatory transcription factor that responds to the allosteric effector molecules? | The Site where the protein binds to the DNA and the site for allosteric effector molecules. |
| What is an operon? | A cluster of genes under transcriptional control of one promoter |
| Why are operons so useful? | They allow a group of genes with a common function to be made at one time |
| What is the lac operon? | In E.Coli, it contains genes for lactose metabolism |
| What is lacP? | The promoter for lac operon |
| What are the 3 structural genes for lac operon? | Lac Z - Beta-galactosidase and allolactose Lac Y - lactose permease Lac A - galactosidase transacetylase |
| What is Lac O? | The operator of lac operon which provides binding site for repressor protein |
| What is the CAP site? | The activator protein binding site for lac operon |
| What is the Lac I gene? | Codes for the Lac repressor, has its own promoter not part of Lac operon |
| What happens when lactose is not present in E.Coli? | The lac repressor protein binds to the nucleotide and prevents transcription from occurring. The RNA polymerase will bind but cannot transcribe. |
| What happens when lactose is present in E.Coli? | 4 allolactose molecule bind to the lac repressor protein and allow RNA polymerase to transcribe the enzyme that digest lactose. |
| What is allolactose? | An allosteric effector molecule |
| What is IPTG? | An artificial inducer of the lac operon that enters the cell without permease lac Y and doesnt need to be converted by permease lac Z (without being transported and doesnt need to be transformed) |
| What are partial diploids? | When F factor from bacteria inserts into the chromosome of a host organism, and is then excised with part of the host organisms chromosome |
| What is a constitutive mutant? | When the transcription is always on |
| What is a non-inducible mutant? | When the transcription can never be on |
| What does it mean when an operator is cis acting? | That it only affect one strand of DNA, not both |
| What does it mean when an operator is trans acting? | That it affects both strands of DNA |
| What is CAP? | A transcription activator |
| What is cAMP? | A small effector molecule that binds to CAP and attaches it to the CAP site on the DNA |
| What happens when there is to much glucose in the system? | It prevents the creation of cAMP which then prevents the binding of CAP to the binding site so transcription does not occur. |
| What is positive control? Give an example. | When the binding of a promoter occurs and transcription is activated. cAMP attaches to CAP which then promotes transcription. |
| What is the trp operon and what is it in? | It is the operon that codes for the amino acid tryptophan, and it resides in E. Coli |
| Why is the trp operon unique? | Because the amino acid, tryptophan, is the product and the repressor for the operon. When levels are low the operon transcribes more of the DNA to produce more tryptophan. When levels are high, tryptophan will be the repressor and shut down transcription |
| Define inducible and give an example. | When a small effector molecule effects an operator and induces transcription. Allolactose |
| Define repressable and give an example. | WHen a small effector molecule effects a repressor and represses transcription. cAMP or tryptophan. |
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24rory
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