Chapter 16; The Jacob-Monod model for gene regulation

pictures of Jacob and Monod ... JacobMonod1965.GIF

 

Regulation of gene activity via the operon

Enzymes may be divided into two categories

Constitutive enzymes are always present

Regulative enzymes may or may not be present

What controls the regulative enzymes; a problem of turning genes on and off???

Answer via mutation analysis

Mutations may be in structural genes (for enzymes) or regulation sequences of DNA

Wild type E. coli will produce the enzyme beta-galactosidase when lactose is present.

Some mutant E. coli will produce beta-galactosidase if lactose is present or absent; they are constitutive mutations

Operon mutation sequence.... ../OperonMutationSeries.html

    Two types of mutations.... OperonMutationsFinal.GIF

    Operon symbols   ../OperonMutationSymbols.gif

            Key genotypes haploid   ../OperonKeyGenotypesHaploid.gif

            Key genoptyes diploid   ../operonKeyGenotypesDiploid.gif

The model:

         Operon series  ../OperonSeries.html 

                Location of the lac operon.... OperonMap.GIF

                Model of a portion of the E. coli chromosome: operon2.GIF

                Concept of the allosteric protein operon3.GIF

                Lactose not present.... operon4.GIF

                Lactose present....operon5.GIF

Simple movie: ... operonmovie.gif


Help for working with the operon

The secret!!   a list of steps..../operonWorkbook2.gif..

A tutorial which may help with the complex genotypes...../Operon%20Tutorial/OperonHome.html

problems from workbook:        ../operonWorkBook.gif



Reality: structure of repressor...OperonModelScience.GIF 

Show cover of Science 1 March 1996      ../../Other%20Graphics/operonCoverScience.gif

Partial DNA sequence for operon (not on web) .. operonDNA

Analysis: Mutations of the lac operon 

 Series 2....../OperonSeries2.html

Mutation in repressor gene i- ... repressorminus.GIF

Mutation in repressor gene is...repressorS.GIF

Mutation in operator oc ... OperatorMutation.GIF

Overview... OperonMutationsOverview.GIF.

...................................................

 

important: repressor protein may act on all chromosomes - trans acting

important: operator DNA cis acting

 

Again, help for working with the operon

The secret!!   a list of steps....../operonWorkbook2.gif

A tutorial which may help with the complex genotypes ../Operon%20Tutorial/OperonHome.html

problems from workbook:      ../operonWorkBook.gif   

 

1 December 2004


two items from the literature


1)  Report on transcription termination in eukaryotes

Tollervey, D. (2004). "Molecular biology: Termination by torpedo." Nature 432(7016): 456-7.

             .....not on the web...../Transcription%20termination.gif


2)  New model for chromosome structure

Two-start helix ...   ../TwoStartHelix.gif

Dorigo picture .. not on web.. ../Dorigo%20picture.gif

so, the solenoid model is out!!

Now, complete the operon model


An early and important idea for gene regulation

An important piece of genetic real estate  -  as in the polylinker for pUC 19

And, there is much more to know about it, but....

In gene regulation we have cis sequences vrs trans acting molecules.

for cis, the effect must a sequence of DNA on the same chromosome

for trans, there is some movable object which may influence another chromosome




To chapter 17    Chapter 17