Regulation of gene expression can occur at the transcriptional and post-transcriptional levels. The Lac operon in E. coli is a classic example of transcriptional regulation, where in the presence of glucose the Lac repressor binds to the operator to repress transcription. However, in the absence of glucose, cAMP activates CAP to bind the DNA and induce transcription, and lactose binds the repressor to further induce transcription. Post-transcriptional control includes mechanisms that regulate RNA processing, transport, stability, and translation.
Includes definition, discovery.Enzyme induction is a process in which a molecule (e.g., a drug) induces (i.e., initiates or enhances) the expression of an enzyme.
The induction of heat shock proteins in the fruit fly Drosophila melanogaster.
The Lac operon is an interesting example of how gene expression can be regulated.
Viruses, despite having only a few genes, possess mechanisms to regulate their gene expression, typically into an early and late phase, using collinear systems regulated by anti-terminators (lambda phage) or splicing modulators (HIV).
Gal4 is a transcriptional activator that controls the expression of GAL1, GAL7, and GAL10 (all of which code for the metabolic of galactose in yeast). The GAL4/UAS system has been used in a variety of organisms across various phyla to study gene expression.
The control of gene expression or protein synthesis is called gene regulation or it is the process of turning genes on and off
Gene regulation in prokaryotes is most extensively observed at the initiation of transcription.
Most genes are controlled by extracellular signals- present in medium.
Repressor, a negative regulatory molecule, binds to the operator gene and interferes with the expression of genes. Activator, a positive regulatory molecule, enhances the expression of the genes.
Operon : a group or cluster of structural genes under a single promoter; bacterial operons are polycistronic transcripts that are able to produce multiple proteins from one mRNA
Francois Jacob and Jacques Monod in 1961
“Lac operon is an operon or a group of genes with a single promoter that encode genes for the transport and metabolism of lactose in E.coli and other bacteria.”
Lac operon concept is an example of prokaryotic gene regulation.
Includes definition, discovery.Enzyme induction is a process in which a molecule (e.g., a drug) induces (i.e., initiates or enhances) the expression of an enzyme.
The induction of heat shock proteins in the fruit fly Drosophila melanogaster.
The Lac operon is an interesting example of how gene expression can be regulated.
Viruses, despite having only a few genes, possess mechanisms to regulate their gene expression, typically into an early and late phase, using collinear systems regulated by anti-terminators (lambda phage) or splicing modulators (HIV).
Gal4 is a transcriptional activator that controls the expression of GAL1, GAL7, and GAL10 (all of which code for the metabolic of galactose in yeast). The GAL4/UAS system has been used in a variety of organisms across various phyla to study gene expression.
The control of gene expression or protein synthesis is called gene regulation or it is the process of turning genes on and off
Gene regulation in prokaryotes is most extensively observed at the initiation of transcription.
Most genes are controlled by extracellular signals- present in medium.
Repressor, a negative regulatory molecule, binds to the operator gene and interferes with the expression of genes. Activator, a positive regulatory molecule, enhances the expression of the genes.
Operon : a group or cluster of structural genes under a single promoter; bacterial operons are polycistronic transcripts that are able to produce multiple proteins from one mRNA
Francois Jacob and Jacques Monod in 1961
“Lac operon is an operon or a group of genes with a single promoter that encode genes for the transport and metabolism of lactose in E.coli and other bacteria.”
Lac operon concept is an example of prokaryotic gene regulation.
Regulation of gene expression in prokaryotes and virusesNOOR ARSHIA
Regulation of gene expression in prokaryotes and viruses includes gene expression mechanism of prokaryotes such as lac operon ,trp operon, feedback inhibition, types of temporal response, positive and negative gene regulation. It also includes mechanisms such as reverse transcriptase in viruses.
Transcription and the control of gene expression [Autosaved].pptxAbdullahAli647576
The first genetic maps, constructed in the organisms
such as the fruit fly, used genes as markers.
• The only genes that could be studied were those
specifying phenotypes that were distinguishable by
visual examination. Eg. Eye color, height.
• Some organisms have very few visual characteristics
so gene mapping with these organisms has to rely on
biochemical phenotypes
Regulation of gene expression in prokaryotes and virusesNOOR ARSHIA
Regulation of gene expression in prokaryotes and viruses includes gene expression mechanism of prokaryotes such as lac operon ,trp operon, feedback inhibition, types of temporal response, positive and negative gene regulation. It also includes mechanisms such as reverse transcriptase in viruses.
Transcription and the control of gene expression [Autosaved].pptxAbdullahAli647576
The first genetic maps, constructed in the organisms
such as the fruit fly, used genes as markers.
• The only genes that could be studied were those
specifying phenotypes that were distinguishable by
visual examination. Eg. Eye color, height.
• Some organisms have very few visual characteristics
so gene mapping with these organisms has to rely on
biochemical phenotypes
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
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This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
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2. Regulation of gene expression
• Gene expression is controlled at:
• A. At transcription level.
• B. At post transcription level.
3. A. Transcriptional control of gene
expression:
• Each differentiated cell has the capacity to
synthesize certain types of protein in suitable
amounts through differential regulation of
gene expression.
• Regulation of gene expression can be
illustrated by the Lac-Operon model in E. Coli
as the simplest model for regulation of gene
expression since regulation of other genes in
E. Coli or eukaryotes are far more complex.
4. Cont------
• Operon is a coordinated unit of gene
expression (Lac = lactose-metabolizing
enzymes, Oper = operation, and On = is on).
• Lac-Operon is formed of two genes with their
regulatory sequences. One gene is
constitutively regulated regulatory gene, the
Lac i-gene, i.e., Lac-gene inhibitory gene that
gives a monocistronic mRNA translated into
the repressor protein.
5. Cont------
• The other gene is structural, Lac-gene formed
of three units (Z, Y and A) and gives a
polycistronic mRNA translated into three
proteins (-galactosidase, lactose permease
and acetylase).
• E. Coli can metabolize glucose, glycerol,
lactose or galactose as a source of energy with
preference to glucose.
6. Cont------
• For the integrated metabolism of lactose the
bacterium requires lactose permease that
permits entry of lactose into the cells
• -galactosidase that hydrolyzes lactose into
glucose and galactose.
• They are co-regulated since they are produced as
one polycistronic mRNA along with a third
enzyme of unknown function, i.e., acetylase(it
may acetylate specific proteins and facilitate gene
induction).
7. Cont------
• Since Lac-gene is an inducible gene, in
presence of glucose the bacterium contains a
few molecules of these enzymes per cell.
• But when the media lacks glucose, the
bacterium expresses this gene at a very high
rate (as much as 100-fold the uninduced rate)
producing large amount of these enzymes per
cell to increase lactose metabolism.
8. lacI
lacZ lacY lacA
CAP binding site Operator (lac repressor binding site)
Promoter (RNA polymerase binding site)
lac Operon
DNA
Promoter
inhibitory gene
promoter operator Structural protein (enzymes - B-galactosidase, Lactose permease and
acetylase)
control genes
Catabolite activator protein
9. Cont------
• Jacob and Monod elucidated the mechanism
of the coordinated regulation of the
expression (induction/repression) of that
Operon in 1961.
• As above, the Lac-gene has a promoter
sequence downstream of which there is the
Operator sequence at which Lac repressor
binds to hinder the binding of RNA
polymerase to the promoter,
10. Cont------
• and upstream of which there is the CAP sequence
at which the catabolite-activated DNA-binding
protein (CAP, cAMP-dependent) binds to activate
binding of RNA polymerase.
• The regulatory Lac repressor DNA-binding
protein is the product of Lac repressor gene (Lac-
I gene) which has the promoter as the only
regulatory sequence and is a regulatory gene
with a constitutive constant rate of transcription
and hence protein synthesis.
Alo-lactose binds to repressor protein to inhibit repression
11. The two states of Lac-Operon
(Repression and induction):
1. Repression:
• When E. Coli is grown in presence of glucose,
transcription of the Lac-gene is repressed.
• Repression is mediated by Lac repressor, which
binds as a tetramer to the operator sequence
preventing the binding of RNA polymerase to the
promoter and prevents the transcription of the
Lac-gene.
• The repressor is a negative regulator, and its
sequence is a silencer on expression of the
Operon
12.
13. 2.Induction (or derepression):
• When glucose is absent, the Lac-gene is
induced, i.e., expression rate of the Operon is
increased.
• Starvation of the bacterium of glucose leads
to increase of cAMP that binds and activates
the DNA binding of the Catabolite gene
Activator Protein (CAP).
14. Cont------
• The CAP binds to the CAP binding sequence
of DNA up-stream the promoter to facilitate
binding of RNA polymerase to the promoter to
induce transcription of the Lac-gene at a low
level.
• Therefore, cAMP-activated CAP is a positive
regulator, and its sequence is an enhancer.
15. Cont------
• The produced small amount of permease
facilitates entrance of lactose into the cell.
• Lactose (an inducer) has high affinity to bind
the repressor causing a change in its
conformation. This change prevents the
repressor from binding to the operator.
• Therefore, lactose acts as an inducer and the
operator becomes free for higher rate of
transcription by RNA polymerase.
16.
17. B. Post-Transcriptional control of gene
expression:
• Gene expression is also regulated at the levels
of RNA processing (e.g., capping, tailing,
alternative splicing and editing), RNA
transport, mRNA half-life and rate of
translation (e.g., proteins utilized in iron
absorption, transport and storage).