Regulation of Gene Expression in Bacteria - MCB 104 Flashcards
Why is it important to learn about Gene expression in Bacteria?
It is important to learn about regulation of gene expression in bacteria because it gives us a general insight in the simplest form, into cell differentiation and embryonic development in animals, as well.
What does gene expression lead to?
When gene is expressed it leads to the formation of proteins that may serve as enzymes, transcription factor , or other regulatory products.
When do bacteria synthesize enzymes? Do they do it continuously regardless of the fact that they need it or not?
Bacteria will only synthesize enzymes necessary to produce compounds only when they cannot obtain the compound from the environment - When there is no other option left. In this way they are economical.
What are two cellular mechanisms important for gene regulation?
Two cellular mechanisms important for gene regulation and that ensure bacteria is being economical are: 1) Cells must be able to recognize environmental conditions in which they should activate or repress the transcription of the relevant genes. 2) Cells must be able to toggle on/off like a switch the transcription of each gene or group of genes.
Why must cells be able to recognize environmental conditions in which they should activate or repress the transcription of the relevant genes?
cells must be able to recognize environmental conditions in which they should activate or repress the transcription of the relevant genes BECAUSE if the compound required by the body is present in the environment then they do not need to activate transcription. Same concept applies to their repression function.
Why must cells be able to toggle on/off like a switch the transcription of each gene or group of genes?
Cells must be able to toggle on/off like a switch the transcription of each gene or group of genes BECAUSE this is how they respond to environmental conditions.
In order to understand gene regulation in bacteria in detail, what is the biological concept that we studied in class?
Metabolism of sugar lactose.
Two types of protein - DNA interactions that regulate transcription?
Two types of protein - DNA interactions that regulate transcription: 1) Where does the transcription begin/occur? [Transcription Initiation] 2) Whether the transcription actually takes place or not. [Transcription]
What protein - DNA interaction regulates where transcription occurs or begins?
Protein - RNA Polymerase II DNA - Promoter Interaction - When RNA Polymerase binds to promoter region, it is an indication that this is where transcription should occur. Transcription begins a few bases away from the promoter region.
Phenotype of Promoter -/-
If the promoter is not present, then transcription cannot take place.
Phenotype of RNA Polymerase II -/-
If the RNA Polymerase II is not present, then transcription cannot take place because RNA polymerase is what drives transcription and produces the relevant mRNA.
What type of protein interaction determines whether promoter driven transcription takes place or not?
Protein - Activators and Repressors DNA - Operator As the name suggests Activators help in activating transcription by helping tether RNA polymerase to the promoter region. And as the name suggests Repressors help in repressing transcription. They do this in two ways: 1) Physically stop RNA Polymerase II from binding to the promoter. [In this way they block transcription initiation] 2) Stop RNA Polymerase II from moving along the DNA chain and carry out transcription. [In this way they actually block transcription]
What are the two types of regulation?
1) Positive Regulation 2) Negative Regulation
What is Positive Regulation?
As the name suggests, it is when a molecule allows transcription to occur. So in this case it will be the activator. When activator binds to its DNA region, it allows the RNA polymerase to bind to the promoter.
NOTE: if you look at the picture, activator has it’s own binding site which is not the operator or the promoter.
What is Negative Regulation?
As the name suggests, it is when a molecule does not allow transcription to occur. So in this case it will be the Repressor protein. When repressor binds to its DNA region (Operator), it blocks transcription from occuring.
But how do activators and repressors respond to environmental conditions? What type of physical change do they undergo that allows them to bind or not bind to their respective binding sites?
In order for activators and repressors to carry out their functions they must be able to bind to their binding sites. They do so by existing in two states:
1) state in which they can bind to the binding site
2) state in which they cannot bind to the binding site.
Structure of each molecule contains two sites on it -
1) the DNA binding domain
2) Allosteric Site
When an allosteric effector binds to the allosteric site it changes the conformation of the DNA binding domain. Which allosteric effector binds to the allosteric site regulates how the DNA binding domain changes - whether is allows the enzyme to get the lock and key conformation or not.
