2.9 Structure And Control Of Gene Exp. Prokaryotes Flashcards
Function of beta-galactosidase (coded by lac z)
hydrolyses lactose into glucose and galactose
Function of lactose permease (coded by lac y)
transports lactose across the cell surface membrane
Function of lactose transacetylase (coded by lac a)
involves in the metabolism of lactose, but exact function is unknown
What is the basic unit of gene expression in prokaryotes?
Operon
True or False: Prokaryotic genes are typically organized in clusters known as operons.
True
Fill in the blank: The __________ is the DNA sequence where RNA polymerase binds to initiate transcription.
promoter
What is the role of the operator in an operon?
It acts as a regulatory sequence that can inhibit or promote transcription.
Multiple Choice: Which component is NOT part of an operon? A. Regulatory Gene B. Promoter C. Structural Genes D. Operator
A. Regulatory Gene
What are the 3 main ways of control for the transcription of an operon?
Inducible, Repressive, Activator Control
True or False: In prokaryotes, the presence of a active repressor protein prevents transcription.
True
Are Enhancers present in prokaryotes?
Enhancers are not present in prokaryotes; they are primarily found in eukaryotic cells.
Fill in the blank: The __________ is a protein that binds to the operator to block RNA polymerase from transcribing the gene.
repressor
What is the function of an inducer in the context of gene expression?
An inducer binds to a repressor, preventing it from blocking transcription.
Multiple Choice: Which of the following is an example of a inducible operon? (inducer can switch operon on!)
Lac operon
Short Answer: What does the lac operon regulate?
The metabolism of lactose in E. coli
True or False: Prokaryotic transcription and translation occur simultaneously.
True
Fill in the blank: The __________ is a sequence in DNA that signals the end of transcription. (in bacteria!)
terminator
What is the role of the CAP protein in the lac operon?
CAP enhances the binding of RNA polymerase to the promoter when glucose levels are low.
Multiple Choice: Which of the following is NOT a feature of prokaryotic gene expression?
Introns
What is the impact of glucose on the lac operon?
High glucose levels reduce the expression of the lac operon to a basal level.
True or False: All prokaryotic genes are expressed at all times.
False
Fill in the blank: The __________ model describes how the lac operon is regulated by the presence or absence of lactose.
inducible
What is a co-repressor?
A small molecule that binds to a repressor protein to activate it, inhibiting transcription.
Multiple Choice: Which of the following processes is responsible for producing mRNA in prokaryotes?
Transcription
Short Answer: What is the primary enzyme involved in prokaryotic transcription?
RNA polymerase
True or False: Prokaryotic genes can be regulated by environmental signals.
True
Fill in the blank: The __________ is a segment of DNA that is transcribed into RNA but not translated into protein.
non-coding region
What is the primary difference between repressible and inducible operons?
Repressible operons are usually on and can be turned off, while inducible operons are usually off and can be turned on.
Multiple Choice: Which of the following is an example of a repressible operon?
Trp operon
Short Answer: What does the trp operon regulate?
The synthesis of tryptophan in bacteria.
True or False: The presence of tryptophan activates the trp operon.
False
Fill in the blank: The __________ region of an operon contains the genes that are co-regulated.
structural
What determines the timing of gene expression in prokaryotes?
Environmental conditions and cellular needs.
Multiple Choice: Which of the following statements about prokaryotic gene expression is true?
It is often regulated at the transcriptional level.
Short Answer: How do prokaryotes respond to changes in nutrient availability?
By regulating gene expression through operons.
What does CAP protein stand for? (regulate lac operon)
Catabolite Activator Protein
Outcome of Active/Inactive Activator Protein?
ACTIVE Activator Protein =>
Transcription is at HIGH RATE.
INACTIVE Activator Protein =>
Transcription is at LOW RATE.
(Sometimes, the rate is slow enough to be
considered negligible / OFF)
Structural genes of trp operon?
trpE, trpD, trpC, trpB, trpA
What is a polycistronic mRNA
Polycistronic mRNA is a type of mRNA molecule, common in prokaryotes, that encodes multiple proteins, rather than just one, and is transcribed from a single promoter and terminator
What regulatory gene codes for the regulatory protein for both lac and trp operon?
trp: trpR, lac: lacl
Lac and trp operon’s control system and the co-repressor or inducer molecule?
Lac: Inducible, inducer is allolactose
Trp: Repressible, co-repressor is tryptophan
Significance of Inducible System and Repressible System
Inducible: Ensures that the cell does not
synthesize nutrient-metabolizing
enzymes until they are needed.
Repressible: Ensures that the cell does not waste energy synthesizing unneeded enzymes.
