Chapter 16 outline
This presentation is the property of its rightful owner.
Sponsored Links
1 / 50

Chapter 16 Outline PowerPoint PPT Presentation


  • 64 Views
  • Uploaded on
  • Presentation posted in: General

Chapter 16 Outline. 16.4 Some Operons Regulate Transcription Through Attenuation, the Premature Termination of Transcription, 442 16.5 Antisense RNA Molecules Can Affect the Translation of mRNA, 445 16.6 Riboswitches Function as Regulatory Elements in mRNAs, 446.

Download Presentation

Chapter 16 Outline

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Chapter 16 outline

Chapter 16 Outline

  • 16.4 Some Operons Regulate Transcription Through Attenuation, the Premature Termination of Transcription, 442

  • 16.5 Antisense RNA Molecules Can Affect the Translation of mRNA, 445

  • 16.6 Riboswitches Function as Regulatory Elements in mRNAs, 446


16 2 many aspects of gene regulation are similar in bacterial and eukaryotes

16.2 Many Aspects of Gene Regulation Are Similar in Bacterial and Eukaryotes


Genes and regulatory elements

Genes and Regulatory Elements

  • Structural genes: encoding proteins

  • Regulatory genes: encoding products that interact with other sequences and affect the transcription and translation of these sequences

  • Regulatory elements: DNA sequences that are not transcribed but play a role in regulating other nucleotide sequences


Genes and regulatory elements1

Genes and Regulatory Elements

  • Constitutive expression: continuously expressed under normal cellular conditions

  • Positive control: stimulate gene expression

  • Negative control: inhibit gene expression


Level of gene regulation

Level of Gene Regulation

  • Many levels at which gene expression may be regulated

    • DNA access

    • Transcription

    • RNA modification and stability

    • Translation

    • Post-translational modification


Dna binding proteins

DNA-Binding Proteins

  • Domains: 60 ~ 90 amino acids, responsible for binding to DNA, forming hydrogen bonds with DNA

  • Distinctive types of DNA-binding proteins based on the motif

    • Motif: within the binding domain, a simple structure that fits into the major groove of the DNA


Concept check 1

Concept Check 1

How do amino acids in DNA-binding proteins interact with DNA?

  • By forming covalent bonds with DNA base

  • By forming hydrogen bonds with DNA base

  • By forming covalent bonds with sugars


Concept check 11

Concept Check 1

How do amino acids in DNA-binding proteins interact with DNA?

  • By forming covalent bonds with DNA base

  • By forming hydrogen bonds with DNA base

  • By forming covalent bonds with sugars


16 3 operons control transcription in bacterial cells

16.3 Operons Control Transcription in Bacterial Cells

  • Operon: promoter + additional sequences that control transcription (operator) + structure genes

  • Regulator gene: DNA sequence encoding products that affect the operon function, but are not part of the operon


Negative and positive control inducible and repressible operons

Negative and Positive Control; Inducible and Repressible Operons

  • Inducible operons: Transcription is usually off and needs to be turned on.

  • Repressible operons: Transcription is normally on and needs to be turned off.


Negative and positive control inducible and repressible operons1

Negative and Positive Control; Inducible and Repressible Operons

  • Negative inducible operons: The control at the operator site is negative. Molecule binding is to the operator, inhibiting transcription. Such operons are usually off and need to be turned on, so the transcription is inducible.

  • Inducer: small molecule that turns on the transcription


Negative and positive control inducible and repressible operons2

Negative and Positive Control; Inducible and Repressible Operons

  • Negative repressible operons: The control at the operator site is negative. But such transcription is usually on and needs to be turned off, so the transcription is repressible.

  • Corepressor: a small molecule that binds to the repressor and makes it capable of binding to the operator to turn off transcription


Negative and positive control inducible and repressible operons3

Negative and Positive Control; Inducible and Repressible Operons

  • Positive inducible operon

  • Positive repressible operon


The lac operon of e coli

The lac Operon of E. coli

  • A negative inducible operon

  • Inducer: allolactose

  • lacI: repressor encoding gene

  • lacP: operon promoter

  • lacO: operon operator


The lac operon of e coli1

The lac Operon of E. coli

  • Structural genes

    • lacZ: encoding β-galactosidases

    • lacY: encoding permease

    • lacA: encoding transacetylase

  • The repression of the lac operon never completely shuts down transcription.


Concept check 4

Concept Check 4

In the presence of allolactose, the lac repressor .

  • binds to the operator

  • binds to the promoter

  • cannot bind to the operator

  • binds to the regulator gene


Concept check 41

Concept Check 4

In the presence of allolactose, the lac repressor .

  • binds to the operator

  • binds to the promoter

  • cannot bind to the operator

  • binds to the regulator gene


Positive control and catabolite repression

Positive control and catabolite repression

  • Catabolite repression: using glucose when available, and repressing the metabolite of other sugars

  • This is a positive control mechanism: The positive effect is activated by catabolite activator protein (CAP). cAMP is binded to CAP, together CAP–cAMP complex binds to a site slightly upstream from the lac gene promoter.


Positive control and catabolite repression1

Positive control and catabolite repression

  • cAMP – adenosine-3′,5′-cyclic monophosphate

  • The concentration of cAMP is inversely proportional to the level of available glucose.


Concept check 42

Concept Check 4

What is the effect of high levels of glucose on the lac operon?

  • Transcription is stimulated.

  • Little transcription takes place.

  • Transcription is not affected.

  • Transcription may be stimulated or inhibited, depending on the levels of lactose.


Concept check 43

Concept Check 4

What is the effect of high levels of glucose on the lac operon?

  • Transcription is stimulated.

  • Little transcription takes place.

  • Transcription is not affected.

  • Transcription may be stimulated or inhibited, depending on the levels of lactose.


The trp operon of e coli

The trp Operon of E. coli

  • A negative repressible operon

  • Five structural genes

    • trpE, trpD, trpC, trpB, and trpA – five enzymes together convert chorismate to typtophane.


Chapter 16 outline

16.4 Some Operons Regulate Transcription Through Attenuation, the Premature Termination of Transcription

  • Attenuation: affects the continuation of transcription, not its initiation. This action terminates the transcription before it reaches the structural genes.


Attenuation in the trp operon of e coli

Attenuation in the trp Operon of E. coli

  • Four regions of the long 5′ UTR (leader) region of trpE mRNA

    • When tryptophan is high, region 1 binds to region 2, which leads to the binding of region 3 and region 4, terminating transcription prematurely.


Attenuation in the trp operon of e coli1

Attenuation in the trp Operon of E. coli

  • Four regions of the long 5′ UTR (leader) region of trpE mRNA

    • When tryptophan is low, region 2 binds to region 3, which prevents the binding of region 3 and region 4, and transcription continues.


Concept check 6

Concept Check 6

Attenuation results when which regions of the 5′ UTR region pair?

  • 1 and 3

  • 2 and 3

  • 2 and 4

  • 3 and 4


Concept check 61

Concept Check 6

Attenuation results when which regions of the 5′ UTR region pair?

  • 1 and 3

  • 2 and 3

  • 2 and 4

  • 3 and 4


16 5 antisense rna molecules can affect the translation of mrna

16.5 Antisense RNA Molecules Can Affect the Translation of mRNA

  • Antisense RNA:

    • Complementary to targeted partial sequence of mRNA


16 6 riboswitches function as regulatory elements in mrnas

16.6 Riboswitches Function as Regulatory Elements in mRNAs

  • Riboswitch: the regulatory sequence of mRNA molecules where molecules can bind and affect gene expression by influencing the formation of secondary structure in the mRNA


  • Login