Genes Flashcards
Define gene
entire DNA sequence required to direct protein synthesis.
What is DNA
The molecule that contains genetic information
What is the size of the human genome in MB?
3200
What is the size of the human gene number
31000
What is the size of the bacteria gene number
4000
What is the size of the bacteria geneome MB
4
What are the basic steps to get from DNA to a protein.
DNA replicates then gene is transcribed then RNA is translated to amino acids to make a protein
What is the label for the binding point for RNA polymerase?
And what are the labels for the bases to the left and to the right of this?
+1 / promotor region
Bases to the left = -ve
Bases to the right = +ve
Which direction on the DNA does the RNA polymerase move?
5’ to 3’
What is the bases at the start and end of the coding region?
Start- ATG
End- TAG or TAA or TGA
If more protein is required how does this affect mRNA synthesis and Protein synthesis
Greater mRNA and Protein synthesis
What are the 2 ways that bacteria control transcription?
Constitutive expressed genes
Regulated genes
How are bacterial promotors recognised by RNA polymerase?
Has a consensus / common pattern of DNA
hexamer (6bp) at -35 and a TATAAT sequence at -10
What is the consensus DNA in a bacterial promotor?
hexamer (6bp) at -35 and a TATAAT sequence at -10
How many types of subunits does the RNA polymerase / holoenzyme molecule have and what are they?
4 types 2 Alpha Beta Beta prime sigma
What are the roles of the subunits in RNA polymerase?
Alpha - enzyme assembly promotor recognition binds to some activators
Beta and Beta prime = catalytic center
sigma= promotor specificity recognising -35 and -10
Describe bacteria Transcriptional initiation
Specific binding at sigma to -35 -10 promoter sequence
DNA unwound at initiation site
Initiation of transcription and release of sigma to elongate.
Describe bacterial elongation
RNA polymerase moves from 5’ to 3’ end of the DNA forming a DNA/RNA hybrid helix before the Nascent RNA is formed 5’ to 3’
Describe bacteria termination
RNA polymerase stops at termination site - TAG or TAA or TGA.
THE RNA polymerase separates and RNA is released
What are the 2 mechanisms of control in transcription in bacteria?
Use of alternative sigma factors
Transcriptional regulators
Name the 2 types of transcriptional regulators
Negative regulation
Positive regulation
Describe negative regulation of transcription
Repressor binds to operator sites to prevent RNA polymerase from binding
Describe positive regulation of transcription
Activators bind to specific site helps RNA polymerase binds
What is the role of the Lac operon?
Switches on genes that encodes enzymes which are needed to metabolise that sugar
Define operon
region of DNA that contains clusters of related genes, made up of promotor region, operator and multiple related genes
What 3 genes make up the lac operon, how many bp and what proteins do they make?
lacZ-3072bp- Beta Galactosidase
lacY-1251bp-Permease
lacA-609bp-Transcetylase
What is the role of Beta Galactosidase
cleaves lactose into its component sugars
What is the role of permease
Transports lactose into cells
What is the role of transacetylase
Covalently modifies lactose
What is the lac operon regulated by?
Negative and positive regulators
Lac repressor,CAP activating protein
Where does the Lac repressor bind and how does it regulate when lactose is absent?
Binds to operator and blocks transcription
Where does the Lac repressor bind and how is it regulated when lactose is present?
Allolactose produced which binds to the lac repressor
This induces a conformational change so repressor cannot bind to the operator
What are transcriptional activators used for?
Allows promorters to be better recognised b y RNA polymerase
What is glucose relationship to the lac operon?
High Glucose- Lac operon off
Low glucose- Lac operon on ( alternative sugar source is lactose)
Describe the CAP/ Catabolite ACtivator Protein function
In low Glucose the cAMP levels are high SO CAP active and Lac operon activated
vice versa for high glucose
