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36 Cards in this Set
- Front
- Back
JACOB AND MONOD
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French researchers
Awarded Nobel Prize for their work on the lac operon |
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LACTOSE METABOLISM IN E.COLI
Preferred Sugar for ATP is: But can use____ if other is absent |
- Glucose
- Lactose (can be used but is less efficient) |
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To utilize lactose as energy source E. coli needs:
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-Beta-galactosidase (cleaves lactose---> glucose and galactose)
-Permease (makes cell wall more permeable to lactose) -Galactoside transacetylase (prevents toxic buildup of lactose products in cell??) |
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E. Coli is most efficient to express enzymes when?
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- Lactose is Available
- And Glucose is unabailable |
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SO..HOW DOES E. COLI Up-regulate gene expression for the 3 enzymes needed...?
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-When lactose is available
-When glucose is unavailable -In a fast and coordinated way |
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Lac Operon System in E. Coli
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Pic
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LAC OPERON IN E.COLI
Since Jacob and Monod’s initial discovery additional research has shown: |
-Three operator regions within promoter
-Repression x1,300 when all three functional (transcription at 1/1300 of level when lactose and cAMP/CAP present) -Loss of individual operators reduces repression level |
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HOW WAS LAC OPERON FUNCTION INVESTIGATED?
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-First gene regulatory system to be understood at molecular level
-Jacob and Monod inserted F’ plasmids into E. coli to create partial diploids (merozygotes) |
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During the Lac Operon Function Investigation what did they find?
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-Inhibitor protein from I gene diffusible
-Functional I gene on one lac operon strand will repress transcription on both (provided both operators unmutated) -Promoter/operator complex only controls genes downstream on same strand -This is cis-dominance |
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Eukaryote's Genome Structure and Organization Characteristics
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-Often multicellular, more complex
-May have multiple copies of genes -Linear DNA complexed with histones -Nuclear membrane separating DNA from cytoplasm -Process primary RNA transcript -mRNA has longer life in cytoplasm -Always have monocistronic mRNA |
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Gene Regulation in Eukaryotes
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Pic
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GENE REGULATION IN EUKARYOTES
Pre-transcriptional |
Gene methylation
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GENE REGULATION IN EUKARYOTES
Transcriptional |
-Hormones as activators
-Enhancers |
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GENE REGULATION IN EUKARYOTES
Post-transcriptional |
Alternate RNA processing
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GENE REGULATION IN EUKARYOTES
Translational |
Masking mRNA
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GENE Methylation IN EUKARYOTES
Methyl group (CH3) added to |
cytosine in
5’-CG-3’ dinucleotides |
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Eukaryotes:
Heavy methylation inactivates |
DNA
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Eukaryotes:
Inactivation reversible if |
methyl groups removed
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Eukaryotes:
Methylated DNA often accumulates |
Mutations
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During Gene Methlaytion of Eukaryotes you have high risks of?
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Permanent inactivation of rarely-transcribed genes
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DOSAGE COMPENSATION
One X chromosome in every somatic cell inactivated by ? |
methylation in female mammals
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DOSAGE COMPENSATION
Males and females have same number of |
active X-linked genes
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Inactivated genes found on the X chromosome in cats such as:
Tortoiseshell Calico Both are XbXo But have different time frames when these genes are inactivated. When does this happen? |
-Calico: X chromosome inactivated early in embryonic development
-Tortoiseshell: X chromosome inactivated later in development |
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TRANSCRIPTIONAL GENE REGULATION : HORMONES
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-Small molecules carried from endocrine cells to target cells
-Target cells contain receptor sites -Most hormones effectors -Possible modes of hormone action: -Bind directly to enhancer or promoter DNA -Bind to/activate effector -Inactivate repressor -Change chromatin structure |
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GENE REGULATION BY STEROID HORMONES
Hormone non-polar |
can pass through cell membrane
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GENE REGULATION BY STEROID HORMONES
Can bind to where? |
Binds in cytoplasm to receptor protein (zinc finger motif)
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GENE REGULATION BY STEROID HORMONES
Receptor protein carries hormone into |
nucleus
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GENE REGULATION BY STEROID HORMONES
Zinc finger binds to An initiates? |
HRE (hormone responsive element) DNA acceptor sequence in nucleus
Transcription |
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GENE REGULATION BY STEROID HORMONES
Diagram |
Pic
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ZINC FINGER MOTIF
Picture |
-Proteins with zinc finger motif bind to DNA
-Polypeptide folded so Zn held between two cysteines and two histidines |
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HRE for estrogen is an
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inverted repeat
5’ AGGTCANNNTGACCT 3’ 3’ TCCAGTNNNACTGGA 5’ |
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TRANSCRIPTIONAL GENE REGULATION: ENHANCERS
Enhancer region can be found? |
upstream or downstream of promoter/structural gene
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TRANSCRIPTIONAL GENE REGULATION: ENHANCERS
Transcriptional activator binds to |
enhancer
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TRANSCRIPTIONAL GENE REGULATION: ENHANCERS
What does DNA do for initiation? |
DNA loops to form transcription initiation complex
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POST-TRANSCRIPTIONAL GENE REGULATION: ALTERNATE RNA SPLICING IN MOUSE ALPHA-AMYLASE
Picture |
pic
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TRANSLATIONAL GENE REGULATION : MASKED mRNA
Unfertilized sea urchin eggs store...... After fertilization proteins removed, and..... |
mRNA complexed with protein, inhibits translation
translation increases 50x |