Your SlideShare is downloading. ×
0
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Regulation of gene expression
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Regulation of gene expression

658

Published on

Lac operon concept

Lac operon concept

Published in: Education, Technology
1 Comment
4 Likes
Statistics
Notes
No Downloads
Views
Total Views
658
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
0
Comments
1
Likes
4
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  1. Regulation of geneexpressionDr. N.R.Hazari
  2.  Gene: A DNA segment that contains theall genetic information required toencodes RNA and protein molecules. Genome: A complete set of genes of agiven species. Gene expression: A process of genetranscription and translation.
  3.  Expression of many genes is relativelycontinuous. Some genes are expressed only under certain conditions, nutritional during differentiation and development after physiological stimulations(nervous,Hormonal etc) stressful situations. Thus there is mechanism by which thecells express or turn off certain genes.
  4.  High cost of protein synthesis, regulationof gene expression is essential to makingoptimal use of energy. Regulation of gene expression isabsolutely essential for the growth,development, differentiation and veryexistence of an organism.
  5.  There are two types of gene regulation 1. Positive Regulation 2. Negative regulation.
  6. Positive regulation The expression of gene isincreased by the presence ofspecific regulatory element ,is saidpositive regulation. The molecule which exert positiveregulation is said to be positiveregulator or activator / inducer The process is called Derepressionor Induction
  7. Negative regulation The expression of gene isdecreased by the presence ofspecific regulatory element ,issaid negative regulation. Molecule which exert the negativeregulation is said to be a negativeregulator or repressor. The process is called Repression.
  8. Sites Gene regulation occurs at thetranscriptional, post-transcriptional,translational and post-translational level. Controlling gene expression is oftenaccomplished by controlling transcriptioninitiation in prokaryotes.
  9.  The environmental and metabolic state ofthe cell has a direct and significant effect onthe control of gene expression. Usually small extracellular or intracellularmetabolites trigger the complex mechanisms. (stimulate or inhibit). All genes are not expressed at all time or inall tissues. Ex: Insulin gene expressed only inpancreatic cells but not in other tissues. Thatmeans insulin gene is in repression state inother tissue.
  10. Type of gene expression Genes or gene expression areconsidered under two categories:1. Constitutive genes or expression: Some genes are essential andnecessary for life, and therefore arecontinuously expressed, such as thoseenzymes involved in TCA cycle. Thesegenes are called housekeeping genes.
  11.  2. Inducible gene or expressionInduction and repressionThe expression levels of somegenes fluctuate in response to theexternal signals.Ex: Tryptophan pyrrolase inducedby tryptophan.
  12. Prokaryotic gene regulation. Prokaryotes provide models for the study ofgene expression in mammalian cells. Some features of prokaryotes geneexpression are unique. In prokaryotes, genes involved in metabolicpathway are often present in linear arraycalled as OPERON. ( mRNA are polycistronic) Multiple genes are present on singletranscript and a single promoter initiates thetranscription all genes.
  13. OPERONFrancois Jacob & Monod in 1961 firstdescribe operon model in E-coli.An operon is a groupof genes that aretranscribed at thesame time.They usually controlan importantbiochemical process.They are found only inprokaryotes.
  14.  Their theory was based on observations oflactose metabolism in E-Coli. When E-Coli cells grown in glucosemedium cells don’t contain β-galactosidaseenzyme. But when cells are transferred to mediumcontain only lactose, then β-galactosidaselevel increases. β-galactosidase hydrolyses the lactose intogalactose & glucose.
  15. Operon The gene for this enzyme isclustered with other two geneswhich produce two enzymes whichare involve in lactose metabolismwith β-galactosidase, i.e.galactoside permease andthiogalactoside transacetylase.
  16.  Genes product involve in the samepathway and initiate the transcription ofthese genes by single promoter andregulate by a single gene called operons. Some operons induced when metabolicpathway needed.For prokaryotic systems:Operon is composed of structural genes,promoter, operator, and other regulatorysequences.
  17. AYZOPIstructural genepermeaseregulatory siteoperatorpromoterCAP-binding siteregulatory genetransacetylaseβ galactosidaseLac Operon
  18. Metabolism of lactose
  19. Adapting to the environment E. coli can use either glucose, which is amonosaccharide, or lactose, which is adisaccharide. However, lactose needs to be hydrolysed(digested) first. So the bacterium prefers to use glucose whenit can present and its genes are constitutive.
  20. Regulation of Lac -operon Four situations are possible1. When glucose is present and lactose is absentthe E. coli does not produce β-galactosidase.2. When glucose is present and lactose is presentthe E. coli does not produce β-galactosidase.3. When glucose is absent and lactose is absentthe E. coli does not produce β-galactosidase.4. When glucose is absent and lactose is presentthe E. coli does produce β-galactosidase
  21. Regulation of lac-operon : glucose ispresent and lactose is absent IN the absences of lactose, the cell hasno need to produce lactose metabolizingenzymes. Hence lac repressor protein , preventsexpression of genes of lactosemetabolism.
  22. AYZOPImRNARNA polSituation I
  23. Situation IIWhen lactose is present, lacZ, lacY, and lacAgenes are expressed.AYZOPIrepressormRNAlactoseallolactoseRNA polgalactosidase
  24. Situation IIIAYZOPI RNA polWhen glucose is present, the [cAMP] is low, no CAP-cAMP isformed and the expression of the lac operon is still low.
  25. Situation 4AYZOPICAPcAMPRNA polWhen glucose is absent and lactose is present, the CAP-cAMP complex binds to the CAP site to activate the lac gene.
  26. CarbohydratesActivatorproteinRepressorproteinRNApolymeraselac Operon+ GLUCOSE+ LACTOSENot boundto DNALifted offoperator siteKeeps fallingoff promotersiteNotranscription+ GLUCOSE- LACTOSENot boundto DNABound tooperator siteBlocked bythe repressorNotranscription- GLUCOSE- LACTOSEBound toDNABound tooperator siteBlocked bythe repressorNotranscription- GLUCOSE+ LACTOSEBound toDNALifted offoperator siteSits on thepromotersiteTranscriptionSummary
  27. THANK YOU!RNA pol

×