Chapter 15 regulation of gene expression
Download
1 / 33

Chapter 15- Regulation of Gene expression - PowerPoint PPT Presentation


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

Chapter 15- Regulation of Gene expression. Regulation is important! Regulation makes sense - the bacteria/cell does the logical, intelligent thing- so you can ask “what would I do if I were a microbe?”, and usually you’ll be right. Lots of wood (fuels)/brick analogies, and stories.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 15- Regulation of Gene expression ' - yestin


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 15 regulation of gene expression
Chapter 15- Regulation of Gene expression

  • Regulation is important!

  • Regulation makes sense- the bacteria/cell does the logical, intelligent thing- so you can ask “what would I do if I were a microbe?”, and usually you’ll be right.

  • Lots of wood (fuels)/brick analogies, and stories.


Some terms
Some terms:

  • Inducible- the environmental effect (specific molecule) turns it (the genes in question) on- e.g., ability to use lactose

  • Constitutive- always on

  • repressible- the environmental effect (specific molecule) turns it (the genes in question) off. e.g.- ability to make tryptophan

  • So genes, or the production of a product, can be considered, inducible, constitutive, or repressible.


Chapter 15 regulation of gene expression

  • These are separate from how the regulation takes place- it can be regulated by:

  • negative control- regulator turns it off.

  • positive control: regulator turns it on.


Selected bacterial operons
Selected Bacterial Operons

OPERON: coordinately regulated genes, usually on the same mRNA in bacteria.

  • By turning genes on and off in response to the environment, the cell works more efficiently, only making gene products needed at that time.

  • Lac operon: catabolism of lactose. 2 enzymes needed:

  • lac permease: brings lactose in

  • β-galactosidase: splits into glucose and galactose.

  • Fuel.


Chapter 15 regulation of gene expression

TWO conditions needed to utilize lactose: 1) lactose has to be there; 2) glucose has to be absent- again, it makes sense!


Chapter 15 regulation of gene expression

Control system: fig 15-1-7: This is the situation when be there; 2) glucose has to be absent- again, it makes sense!no glucose is present, and lactose induces the operon. Please study these figures!!!!


Chapter 15 regulation of gene expression

Lactose (actually, allolactose- is really much smaller Allostearic interaction

Repressor acts negatively to inhibit transcription.

www.prenhall.com/klug, http://vcell.ndsu.nodak.edu/animations/home.htm


Chapter 15 regulation of gene expression

Proof: isolation and behavior of Allostearic interactionconstitutive mutants, such as Oc and lacI-, and dominance/recessive behavior as merodiploids. Table 15.1 Also biochemistry- isolation of repressor protein, binding characteristics to operator, etc.


Chapter 15 regulation of gene expression

However, good repressor will work, so an I Allostearic interaction-/I+ merodiploid will be regulated.



Chapter 15 regulation of gene expression

A superrepressor (I Allostearic interactions) will bind, shutting off transcription, no matter what- it will be dominant over an I+


Cap protein and positive regulation
CAP protein and positive regulation Allostearic interaction

  • When glucose is in abundance, the lac operon is not turned on, even when lactose is present! Makes sense!

  • Regulation involved CAP, cAMP, and RNA polymerase

  • CAP: catabolite activator protein: stimulates transcription when cAMP levels are high.


Chapter 15 regulation of gene expression

  • cAMP: Fig. 15-9: Formed when glucose levels are low. The enzyme that produces cAMP (adenyl cyclase), is inhibited by allosteric interaction with glucose. Thus as glucose levels fall, the enzyme is more active, cAMP levels rise.

  • CAP + cAMP bind to promoter, turns weak promoter into STRONG promoter!


Chapter 15 regulation of gene expression

CAP is kind of like a transcription factor- + acting, stimulating transcription

CAP regulates probably 50 genes- NO sugar or other carbon source would be used, as long as glucose is there!


Tryptophan biosynthesis
Tryptophan biosynthesis stimulating transcription

  • Trp: amino acid; (= “bricks”); building block.

  • trp operon: genes for making tryptophan.

  • trp is on when tryptophan levels are low; off when levels are high.


Chapter 15 regulation of gene expression

MORE allosteric interaction! stimulating transcription


Chapter 15 regulation of gene expression


Gene regulation in eukaryotes
Gene regulation in eukaryotes stimulating transcription

  • I. Some considerations: (Fig. 15-12)

  • a. lots more DNA; chromatin has histones, which have to be considered. Chromatin can be available for transcription (decondensed) or unavailable (condensed), which makes a BIG difference!

  • b. transcription in the nucleus, translation in the cytoplasm

  • c. processing: caps, tails, splicing. Alternative splicing!

  • d. long half-life of mRNA in our cells! in bacteria, it’s about 3 min; ours is 20 min or longer.

  • e. cell differentiation: not only environment, but cell type influences gene expression. (i.e., no hairy livers!)


Lots of transcription factors
Lots of transcription factors! stimulating transcription

  • The regulatory regions can be VERY complex!! Fig. 15-18


What do transcription factors really look like

What do transcription factors really look like? stimulating transcription

There are recurring patterns, called motifs – the beta barrel is one of those others…


Chapter 15 regulation of gene expression

Here’s a very simple eukaryotic regulation path. Steroids, unlike other hormones, take a long time to work an do so by affecting transcription. The hormone-receptor scale is WAY off.


Chapter 15 regulation of gene expression

Ways to make multiple proteins form the same gene Steroids, unlike other hormones, take a long time to work an do so by affecting transcription. The hormone-receptor scale is WAY off.


Chapter 15 regulation of gene expression

Just to amaze you… Steroids, unlike other hormones, take a long time to work an do so by affecting transcription. The hormone-receptor scale is WAY off.


The quiz ignore
The quiz (ignore) Steroids, unlike other hormones, take a long time to work an do so by affecting transcription. The hormone-receptor scale is WAY off.

  • Lac operon!!! Q’s 4 & 5 in the homework- stuff like that

  • Examples of allostearic interactions

  • Simple statements about CAP, TRP


ad
  • Login