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40 Cards in this Set
- Front
- Back
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Describe how RNAP interacts with binding sites upstream from DNA promoter region. |
RNAP grips DNA at binding sites -10 / -35 from start codon. Closer binding site is to consensus, higher affinity for RNAP; Increased Transcription Rate. |
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What would be the consensus for genes: A T C G T G T C A A A T C A A A T C A C |
ATCA |
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Define Polycistronic and Monocistronic. |
Polycistronic: Region of DNA encodes for multiple proteins that serve an overlapping function. Monocistronic: One gene encodes for one protein. |
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Describe Promoter Regions. |
Sections of DNA that tell RNAP initiate transcription |
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Describe Terminator Regions. |
Sections of DNA that tell RNAP where to end transcription. |
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What happens at the -10 binding site (bacterial) upstream to initiate Transcription. |
Melting of the DNA. |
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Describe properties of the -10 binding site that makes it appropriate binding site. |
Base pairs slanted, bases more exposed. Occurs on both sides of DNA: Propeller Twist Sizes of Pyrimidines/Purines uneven; alternating causes instability. |
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What properties can the -10 binding site have to maximise transcription rate? |
AT pairings (only 2 hydrogen bonds) Alternating Pyrimidine/Purines |
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The closer the binding site to the consensus... |
The stronger the affinity for RNAP to bind. |
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Describe NEGATIVE control regulation. |
Promoter active in absence of regulatory protein Regulators > Promoters; Inhibits RNAP initiating transcription. |
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Describe POSITIVE control regulation. |
Promoter inactive in absence of regulatory protein. Regulators > Activator Binding Site; Assist RNAP to bind at promoter and initiate transcription. |
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Describe 2 ways of regulating Negative control. |
Inducible: Inducer binds/inactivates Repressor. Repressible: Co-repressor needed for Repressor function. Can dissociate to inhibit. |
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Give an examples of genes using Inducible/Repressible Negative Controls |
Inducible: Lac Operon Repressible: Trp Operon |
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Describe regions of Lac Operon. |
Inducer - ... - Promoter - Operator - LacZ - LacY - LacA |
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What do LacZ - LacY - LacA encode for? |
LacZ - Beta-glycosidase Lac Y - Permease Lac A - Transacetylase |
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Describe how LacI (Inducer) regulates Lac Operon. |
Encodes for mRNA and production of Repressor. Inhibition of Operator, RNAP cannot bind. |
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Describe how the Lac-operon causes a activation cascade. |
RNAP > mRNA for multiple genes (Z,Y,A) > Multiple ribosomes > Multiple Proteins. |
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Describe Function of Beta-Galactosidase |
Converts Lactose > Galactose + Glucose. |
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Describe function of IPGT. |
Used to turn off Lac Operon by binding to repressor instead of lactose, more efficient. |
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What conditions are required for lactose to be used as a carbon source? |
Lactose present in environment No glucose in envronment. |
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What is the wildtype for Lac Operon (O,Z,Y) |
O+,Z+,Y+ Z/Y induced |
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What does the partial diploid O+Z+Y+/F' O+Z-Y+ express? |
O+,Z+,Y+ Z/Y induced Z+ dominant over Z- |
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What does Oc Z+Y+ express? |
Z+/Y+ express ALL the time. Due to altered Oc site that cannot bind suppressors |
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What is the heterozygote O+/Oc an example of? |
Cis-acting. Oc binding site altered, X/Y expressed constantly, despite wildtype O+ being induced. |
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What is the heterozygote I+/I- an example of? |
Inducible. Wildtype I+ can induce both DNA strands, despite I- not producing it's own suppressor. |
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What is the heterozygote I+/Is an example of? |
Trans-dominant Mutation. Is produced modified suppressor that cannot bind inhibitors. Operator region constantly induced. |
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Describe what happens in a F'wt / wt Lac operon genome when lactose but not glucose is present. |
Lactose binds to repressor, preventing binding to Operator. Allows RNAP to bind and synthesise mRNA. |
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What do low levels of glucose result in the synthesis of? |
cAMP |
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Describe the mechanism of cAMP-CRP. |
Read cram notes. |
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What is the ground state for Bacteria and Eukaryotes? |
Bacteria: ON, Activator Protein + RNA P Eukaryotic: OFF, DNA coiled into Nucleosomes. |
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Describe the 3 types of RNAP. |
RNAP I - Synthesise rRNA RNAP II - Synthesise mRNA RNAP III - Synthesise tRNA |
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Describe Eukaryotic Transcription Complexity. |
Transcription factors needed in addition to RNAP II. 3 types of RNAP. Activators/Repressors can bind several kb away from Promoter region (Enhancers) Transcription must be done Chromatin structure. |
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Describe Enhancers. |
Promoter elements that precede promoter. E.g. TATA box Needed to initiate transcription; do not regulate. |
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Describe Mega-Dalton Complex. |
Involves Transcription Factors + RNAP II In vivo, due to chromatin structure. Requires help of activation proteins, Induces initiation. |
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Describe pathway of initiation in Eukaryotes. |
Activators > Alter Chromatin Structure. Enhancer sequences > Help bind Transcription Factors + RNAP to DNA. |
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Describe the Gal Pathway. |
See cram cards. |
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Describe Nucleoside Remodelling. |
See cram cards. |
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Describe Histone acetylation. |
Lysine-NH2 + Acetyl-CoA > Lysine NH-CO-CH3 |
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How can you switch on/off system via Chromatin remodeling? |
Histone Acetylation: Turns on; Via Gal4 Histone Deacetylation: Turns off; Via presence of glucose. Stimulates Deacetylase (TUP1) to binding site (MIG1), reverting acetylation. Methylation: Methylated DNA associated iwth inactivity. C residues in CpG methylated. |
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Describe Epigenetics. |
Inherited traits involved in gene expression control do not depend on DNA sequence changes. E.g. Acetylation/Methylation of Histones can be inherited. Environment can cause inheritable epigentic marks. |
