Upgrade to remove ads
lac vs trp operon
Terms in this set (60)
When is the lac operon used?
In the absence of glucose AND the presence of lactose.
When lactose is present, transcription _____
When lactose is absent, transcription _____
does not occur
When lactose is absent, the repressor is _____ and _____ to the operator
When lactose is present, the repressor is _____ and _____ to the operator
inactive, cannot bind
When lactose is absent, RNA polymerase _____ bind to the promoter
When lactose is present, RNA polymerase _____ bind to the promoter
When lactose is present, the lac repressor ______ transcription
When lactose is absent, the lac repressor _____ transcription
does not allow
What acts as a lactose sensor?
The lac operon
What acts as a glucose sensor?
The catabolite activator protein (CAP)
What are the structural genes on the lac operon?
lacZ, lacY, lacA
breaks down lactose into glucose and galactose
encodes lactose permease
transports lactose into the cell
acetylates lactose as it is taken up by the cell
codes for lac repressor; located 1/4 away on the chromosome from the lac operon; has its own promotor, negatively regulates the lac operon
Allolactose levels _____ in the presence of lactose
Repressible enzymes usually function in _____ pathways.
Inducible enzymes usually function in _____ pathways.
A process in which large molecules are built from small molecules
A process in which large molecules are broken down
CAP binding site
A positive regulatory site that is bound by catabolite activator protein (CAP). When CAP is bound to this site, it promotes transcription by helping RNA polymerase bind to the promoter.
a small molecule that binds to a bacterial repressor protein and changes the protein's shape, allowing it to bind to the operator and switch an operon OFF. EX: tryptophan (inactive --> active)
Inducer of the lac operon; isomer of lactose generated by b-galactosidase
A specific small molecule that binds to a bacterial repressor protein and changes the repressor's shape so that it cannot bind to an operator, thus switching an operon ON. ex: allolactose (active --> inactive)
What does CAP do?
Binds to a region of DNA just before the lac operon promoter and helps RNA polymerase attach to the promoter, driving high levels of transcription.
What is cyclic AMP?
A "hunger signal" made by E. coli when glucose levels are low; secondary messenger in cell signaling. cAMP binds to CAP, changing its shape and making it able to bind DNA and promote transcription. Without cAMP, CAP cannot bind DNA and is inactive.
When glucose levels are low, cAMP levels are _____, and CAP is _____
When glucose levels are high, cAMP levels are _____, and CAP is _____
Transcription levels are low when glucose levels are _____, cAMP levels are _____, and CAP is _____
high, low, inactive
Transcription levels are high when glucose levels are _____, cAMP levels are _____, and CAP is _____
low, high, active
Glucose present and lactose absent results in _____ transcription
No transcription; CAP cannot bind; repressor binds
Glucose present and lactose present results in _____ transcription
low levels of; CAP cannot bind; repressor cannot bind
Glucose absent and lactose absent results in _____ transcription
No transcription; CAP binds; repressor binds
Glucose absent and lactose present results in _____ transcription
high levels of transcription; CAP binds; repressor cannot bind
The lac operon is usually in the ______ position and is a(n) _____ operon
The trp operon is usually in the ______ position and is a(n) _____ operon
When tryptophan levels are low, the operon is _____
When tryptophan levels are high, the operon is _____
When the trp repressor is bound, the operon is _____
If tryptophan is present, then the trp operon is turned _____
If tryptophan levels are low, then the trp operon is turned _____
on (then the genes are transcribed, enzymes are made, and more tryptophan is made)
What are the genes of the trp operon?
trpE, trpD, trpC, trpB, trpA
When the trp repressor binds to the operon, transcription _____ occur
When the trp repressor does not bind to the operon, transcription _____ occur
If tryptophan is present, then the repressor _____ bind to the operon
When there is little tryptophan, the repressor is _____
When there is lots of tryptophan, the repressor is _____
What is attenuation
a mechanism for reducing expression of the trp operon when levels of tryptophan are high by preventing completion of transcription
Attenuation causes RNA polymerase to _____
stop transcribing prematurely
A section of the operon located between operator and the first gene; encodes a short polypeptide and also contains an attenuator sequence
a sequence found in certain operons in bacteria that stops transcription soon after it has begun; does not code for a polypeptide, but has complimentary sections and can form into a loop; 14 amino acids long with two trps
Protein or DNA sequence that inhibits the termination of transcription; keeps transcription going
When tryptophan is abundant, the ribosome moves _____ along the leader, the _____ forms, and transcription of the trp operon ______.
quickly; terminator hairpin; ends
When tryptophan is scarce, the ribosome moves _____ along the leader, the _____ forms, and transcription of the trp operon _____.
slowly; non-terminator hairpin; continues
The hairpin loops is between
3 & 4
in prokaryotes, increase the variability of gene products from one transcript (starting transcription in different sites within the gene leads to different gene products).
THIS SET IS OFTEN IN FOLDERS WITH...
ungraded hw chapter 11
ungraded hw chap 12 + 13
YOU MIGHT ALSO LIKE...
lect. 25 quiz
BIOL 2170 Lecture 25 Quiz (Ch. 19)
Genetics Exam 3 Review Ch. 14
The Lac Operon
OTHER SETS BY THIS CREATOR
ellis- first 5 commandments study guide
plurals of words
articles changing in plural
articles of countries
OTHER QUIZLET SETS
Genetics Unit 3 homework
FTM: Gene Regulation
Neuropharm Exam 1 Spring
BS 161 - Exam 4 - Lecture 27 (Control of Gene Expr…