Ambe 101 @ lec 9-trp operon
- 1. B A C T E R I A L G E N E T I C S : T r p O P E R O N L E C T U R E - 1 0
- 2. The tryptophan operon is the regulation of transcription of the gene responsible for biosynthesis of tryptophan from chorismite. Trp operon can define as a repressible system, which regulates the gene expression for the biosynthesis of tryptophan according to the binding or uncoupling of a repressor with the operator region. The association and dissociation of the repressor protein strongly depend upon the tryptophan level in the surrounding.
- 3. High level of tryptophan or effector molecule escalates the binding affinity of a repressor protein with the operator sequence, which in turn terminates the gene transcription. In contrast, a low level of tryptophan results in detachment of the repressor from the operator region and allows gene expression.
- 5. It is the region on a bacterial chromosome that comprises a specific nucleotide sequence, where an RNA polymerase can specifically bind to initiate transcription. The binding of a repressor protein with the operator inhibits the binding of RNA polymerase with the promoter sequence, which in turn terminates the transcription. PROMOTOR GENE
- 6. It is the specific nucleotide sequence on chromosomal DNA of E.coli, where a repressor protein can bind by the association of an effector molecule or tryptophan. Here, the tryptophan molecule works as a corepressor that aids activation of aporepressor protein. OPERATOR GENE
- 7. REGULATOR Y GENE Tryptophan operon is a repressor system, in which a regulatory gene of chromosome encodes trp repressor protein that recognizes the operator sequence. The repressor protein switch on the operon system at low trp level in the surrounding, while switching off the system at high trp level in the environment. Therefore, a repressor protein is associated with the synthesis of five gene products mediated by the level of tryptophan in the surrounding. A repressor becomes active or inactive by the presence or absence of corepressor or effector molecule (tryptophan).
- 8. ATTENEUTOR REGION It is found in the middle of operator region and structural genes. Attenuator region comprises leader sequences (160bp in size) that regulate the transcription via attenuation. Its mechanism is to attenuate the efficiency of transcription at sufficient tryptophan inside the bacterial cell by the formation of dimers. Oppositely, the RNAp can traverse through the attenuator region and can transcribe the genes necessary for trp construction, at low tryptophan level.
- 9. In tryptophan operon, there are five structural genes, namely Trp A, B, C, D and E. The structural genes encodes for the enzymes and its subunits important for the biosynthesis of tryptophan from chorismic acid. STRUCTURAL GENES
- 11. R E G U L AT I O N O F t r p O P E R O N
- 20. Explain about repressible operon? What is gene regulation and explain the induction and repression of gene regulation in prokaryotes? Write the difference between inducible and repressible operons? Write the difference between lac operon and trp operon?