Regulating Gene expression

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At what levels can gene expression be controlled at ?
Transcriptional, post-transcriptional and post-translational level
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How is gene expression controlled at the transcriptional level?
By altering the rate of transcription of genes which is controlled by transcription factors
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What is a transcription factor ?
proteins that bind to DNA and switch genes on or off by increasing or decreasing the rate of transcription. Factors that increase rate of transcription=activators. Factors that decrease transcription rate=repressors
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What determines weather a transcription factor can bind to dna
The shape of the transcription factor which can be changed by the binding of some molecules. therefore the amount of certain molecules in an environment or a cell can control the synthesis of some proteins by affecting transcription factor binding.
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Where on DNA do transcription factors bind in eukaryotes?
To specific DNA sites near the start of their target genes.
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Where on DNA do transcription factors bind in prokaryotes?
to operator regions of an operon
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What is an Operon?
A section of DNA that contains a cluster of structural genes, that are transcribed together, as well as control elements and a regulatory gene.
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What do the control elements include?
a promoter (DNA sequence located before the structural genes that RNA polymerase bind to) and an operator (a DNA sequence that transcription factors bind to)
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What does the regulatory gene do?
codes for an activator or repressor
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What are the 3 structural genes in the operon of E.coli?
lacZ, lacY, lacA they produce proteins that help the bacteria digest lactose
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How does the lac operon work when lactose isn't present?
The regulatory gene (lacl) produces the repessor, which is a transcription factor that binds to the operator site when there is no lactose present. This blocks transcription as RNA polymerase cant bind to the promoter.
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How does the lac operon work when lactose is present?
Lacotse binds to the repressor, changing its shape so it can no longer bind to the operator site. RNA polymerase binds and begins transcription of the structural genes.
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How is mRNA edited at post-transcriptional level?
1.mRNA strand that contains introns(don't code for proteins) and exons (code for proteins) is called primary mRNA transcrips 2.Introns are removed by splicing (introns removed and exons joined) 3. mature mRNA leaves nucleus for next stage.
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How does cAMP activate PKA enzyme at post-translational level
1.some proteins (pka) aren't active straight after translation and need to be activated. 2.PKA is an enzyme made of 4 subunits 3. four units are bound together and inactive 4. cAMP binds=changes 3D structure, releasing active subunits = PKA active
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What is a body plan?
The general structure of an organism- body parts arranged in a particular way
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What controls the development of a body plan?
Proteins- help set uop basic body plan so that so that everything is in the right place.
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What are the genes that code for these proteins called?
Hox genes
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What evidence shows body plan development is controlled in a similar way in animals, plants and fungi?
They all have similar Hox genes
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What are homeobox sequence?
regions of the Hox genes. They are highly conserved= sequences change very little during the evolution of different organisms that poses the sequences.
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How do Hox genes control development?
1. Homeobox sequences code for part of the protein= homeodomain 2. Homeodomain binds to specific sites on DNA =protein can work as a transcription factor. 3.Proteins bind to DNA activating/repressing transcription= altering body plan development
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What is apoptosis?
Highly controlled process where some cells die and breakdown =normal part of development
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what happens when apoptosis is triggered?
1.enzyme in cell break down important cell components 2.as cell contents are broken down it shrinks and breaks up into fragments. 3.cell fragments are engulfed by phagocytes and digested
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During development which genes are switched on/off?
genes that control apoptosis and mitosis switch on /off in appropriate cells. this means some cells die and some new cells are produced and so the correct body plan develops.
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give and example of an internal stimulus that will effect the genes that control the cell cycle and apoptosis?
DNA damage- if detected in cell cycle can result in expression of gene which cause cell cycle to pause and trigger apoptosis
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Give an example of an external stimulus that will effect the genes that control apoptosis and m[the cell cycle?
stress caused by lack of nutrient availability- result in gene expression that prevents cells undergoing mitosis.
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What are the three types of DNA mutation?
1.substitution-one or more bases swapped 2.Deletion-one or more babes removed 3. insertion- one ore more bases are added
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When would a mutation have a neutral effect?
1. codes for same protein 2.new triplet codes for different amino acid but it has similar chemical properties so functions like original 3.the mutated triplet codes for an amino acid not involved in with the proteins function
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When would a mutation have a beneficial effect?
when it has an overall advantageous effect on an organism- increases chance of survival
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When would a mutation have a harmful effect?
When it has an overall disadvantages effect on an organism and decreases its chance of survival
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How is gene expression controlled at the transcriptional level?

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By altering the rate of transcription of genes which is controlled by transcription factors

Card 3

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Card 4

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What determines weather a transcription factor can bind to dna

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Card 5

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Where on DNA do transcription factors bind in eukaryotes?

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