What are the components of an operon? What important regulator is not part of the actual operon? Know how operons are classified and how each type works (Inducible, Repressible, Positive, Negative.)© BrainMass Inc. brainmass.com October 25, 2018, 3:51 am ad1c9bdddf
1.What are the components of an operon? What important regulator is not part of the actual operon?
The components of the operon include:
? The regulatory gene codes for the repressor protein.
? The promoter site is the attachment site for RNA polymerates.
? The operator site is the attachment site for the repressor protein.
? The structural genes code for the proteins.
? The repressor protein is different for each operon and is custom fit to the regulatory metabolite. Whether or not the repressor protein can bind to the operator site is determined by the type of operon.
? The regulatory metabolite is either the product of the reaction or the reactant depending on the type of operon.
? The messenger RNA.
? The final enzyme. (library.thinkquest.org/28751/review/genetics/7.html)
Regulatory genes need not be part of the operon itself, but may be located elsewhere in the genome.
2. Know how operons are classified and how each type works.
In genetics, an operon is a functioning unit of genomic material that contains a cluster of genes under the control of a single regulatory signal or promoter (Jacob, Perrin, Sanchez, & Monod, 1960).
Operons are classified as follows:
This posting shows how operons are classified and how each type works. References are also provided to justify the assertions.
Schematic of the Lac Operon
See the attached file.
Below is a schematic of the lac operon:
SHAPE * MERGEFORMAT
A special class of mutants of E coli unable to utilize lactose as a carbon source were found to have mutations in the coding sequence for β-galactosidase (lacZ gene). They produce no β-galactosidase protein. Surprisingly, they fail to produce the polypeptide products of the permease (lacY) and the transacetylase (lacA). In addition, no mRNA from any of these genes is detected.
Three kinds of revertants were isolated:
Type I Revertants: Regained permease (LacY) and transacetylase (LacA) activities but not β-galactosidase activity. These reverting mutations were found within the lac operon.
Type II Revertants: Regained all 3 enzymatic activities.
Type III Revertants: Regained only permease and transacetylase activities by a secondary mutation that mapped in the gene for rho factor.
Lac operon DNA was isolated from the original mutant strain. The strands of the DNA were separated from each other and mixed with single strands of DNA containing the lac operon isolated from a wild type bacterium. These "mixed" DNAs were allowed to hybridize to each other. The resulting double helix structures were isolated and visualized via electron microscopy:
SHAPE * MERGEFORMAT A. (5pnts) What is a revertant mutation (in general)?
B. (5pnts) What was the genetic event that caused the original lac- mutation (ie did not allow for the expression of lacZ, lacY, or lacA)?
C. (5pnts) Why did this event result in failure to produce permease and transacetylase?
D. (5pnts) What is the nature of the Type I Reverting mutations?
E. (5pnts) What is the nature of the Type II Reverting mutations?
F. (5pnts) What is the nature of the Type III Reverting mutations?View Full Posting Details