1. Watch this video
2. Study this summary
General Overview:
- Operons are defined as clusters of genes transcribed as a single RNA. However, for AP Bio students, their key importance is as bacterial gene regulation systems. They’re rare in eukaryotes, which (as we’ll see in the next tutorial) use other means for regulating gene expression.
- Components of an operon:
- Structural Genes: Code for proteins.
- Promoter: Where RNA polymerase binds to initiate transcription.
- Operator: A DNA sequence where repressor proteins bind to regulate transcription.
- Regulatory Gene: Produces a repressor protein that interacts with the operator.
The Trp Operon (Repressible Operon):
- Function: Synthesizes tryptophan (an amino acid) only when it’s not available in the environment.
- How it works:
- When tryptophan is absent:
- The repressor protein cannot bind to the operator.
- RNA polymerase transcribes structural genes, producing enzymes for tryptophan synthesis.
- When tryptophan is present:
- Tryptophan binds to the repressor protein (acting as a co-repressor).
- The repressor changes shape, binds to the operator, and blocks transcription.
- When tryptophan is absent:
- Key Rule: If tryptophan is present, don’t make it. Saves energy.
The Lac Operon (Inducible Operon):
- Function: Produces enzymes that digest lactose when lactose is available.
- How it works:
- When lactose is present:
- Lactose binds to the repressor protein, changing its shape so it cannot bind to the operator.
- RNA polymerase transcribes structural genes, producing enzymes to break lactose into glucose and galactose.
- When lactose is absent:
- The repressor protein binds to the operator, blocking transcription.
- When lactose is present:
- Key Rule: If lactose is absent, don’t make enzymes to digest it. Saves energy.
- Inducer: Lactose turns on the operon.
Operons and Negative Feedback:
- Trp Operon:
- Transcription starts when tryptophan is absent.
- Tryptophan production eventually represses its own synthesis (negative feedback).
- Lac Operon:
- Lactose presence activates transcription.
- Lactose digestion reduces lactose levels, turning off the operon (negative feedback).
Glucose vs. Lactose Metabolism (AKA Diauxic Growth)
- When provided with glucose and lactose:
- E. coli prefers glucose as it’s easier to metabolize (monosaccharide v. disaccharide)
- When glucose runs out, there’s a lag while the lac operon activates and produces enzymes to digest lactose.
3. Master these flashcards
[qdeck style=”width: 600px !important; min-height: 450px !important;” flip_direction=”random” bold_text=”false” “]
[h] Operons Flashcards
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|18658f7e1c110″ question_number=”232″ topic=”6.5.Regulation_of_Gene_Expression”] What is a promoter?
[a] A promoter is a DNA sequence where RNA polymerase (RNAP) can bind to initiate transcription. The promoter is always upstream from the gene.
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|185bf4cd0f910″ question_number=”234″ topic=”6.5.Regulation_of_Gene_Expression”] What’s an operon?
[a] An operon is a group of genes transcribed in a single mRNA molecule, which can then be translated into multiple proteins, all of which are part of the same metabolic pathway or process. Operons generally involve a regulatory system in which the expression of the operon is under the control of a regulatory protein that interacts with an operator region near the operon’s promoter (the details of which are covered in several other cards).
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|1853a962b3510″ question_number=”235″ topic=”6.5.Regulation_of_Gene_Expression”] Explain the difference between an inducible operon (like the lac operon) and a repressible operon (like the trp operon)
[a] Inducible operons are turned “on” (induced) by the presence of a metabolite. For example, the lac operon is induced by the presence of lactose, which turns the operon “on.” When all the lactose is digested, the operon switches off (and no longer produces enzymes for lactose digestion).
Repressible operons are turned “off” (repressed) by the presence of a metabolite. For example, when there’s no tryptophan in the environment, the trp operon turns “on,” and the cell produces enzymes needed for tryptophan synthesis. When tryptophan is present it represses the operon.
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|1843f21270510″ question_number=”236″ topic=”6.5.Regulation_of_Gene_Expression”] Explain how the lac operon works when lactose is absent from E. coli’s environment.
[a] The lac operon is an inducible operon, consisting of a regulatory gene (1), a promoter (5), an operator (6), and structural genes (7). The structural genes code for enzymes that digest lactose into monosaccharides. When lactose is absent, the regulatory protein (3) binds to the operator region (6), which blocks RNA polymerase (4), preventing it from transcribing the structural genes (7).
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” topic=”6.5.Regulation_of_Gene_Expression” dataset_id=”AP_Bio_Flashcards_2022|a0586d636189″ question_number=”237″] Explain how the lac operon works when lactose is present in E. coli’s environment.
[a] When lactose (8) is present in the cell’s environment, it diffuses into the cell and binds with the lac regulatory protein (3). Binding causes an allosteric change in the protein (3a), making it unable to bind with the operator region (6). With the operator unblocked, RNA polymerase can transcribe the genes for lactose digestion (7a – 7c).
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” dataset_id=”AP_Bio_Flashcards_2022|183ac7239e910″ question_number=”238″ topic=”6.5.Regulation_of_Gene_Expression”] Explain how the trp operon works when the amino acid tryptophan is not present in E. coli’s environment.
[a] The trp operon is repressible, consisting of a regulatory gene (1), a promoter (5), an operator (6), and structural genes (7a – 7e), which produce enzymes that synthesize the amino acid tryptophan. When tryptophan is absent, the regulatory protein cannot bind with the operator. Because the operator isn’t blocked, RNA polymerase (4), can transcribe the structural genes.
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” topic=”6.5.Regulation_of_Gene_Expression” dataset_id=”AP_Bio_Flashcards_2022|9eb300fb2d89″ question_number=”239″] Explain how the trp operon works when the amino acid tryptophan is available in E. coli’s environment.
[a] When tryptophan (8) is available in the cell’s environment, it diffuses into the cell and binds with the trp regulatory protein (3). This causes an allosteric change in the trp regulator so that it binds with the operator region (6), blocking RNA polymerase from transcribing the genes for tryptophan synthesis.
[q json=”true” yy=”4″ unit=”6.Gene_Expression_and_Regulation” topic=”6.5.Regulation_of_Gene_Expression” dataset_id=”AP_Bio_Flashcards_2022|9dabe7bb8989″ question_number=”240″] The lac operon system works through negative feedback. Explain.
[a] The lac operon system is an inducible operon. When lactose is present it binds with the regulatory protein, causing an allosteric shift that keeps that protein from binding with the operator, permitting transcription to occur. When all the lactose is digested, the regulatory protein reverts to its unbound shape, enabling it to bind with the operator again, blocking transcription. Thus, the entire system is a negative feedback system in which the activity of the system has the effect of turning the system off.
[q]Connect how operons work to the phenomenon of diauxic growth.
[a]During the 1st growth phase, the bacteria are consuming the easier-to-digest glucose, but not lactose. The evidence for this is that the glucose concentration (X) is going down, while the lactose concentration (Y) stays constant. When the glucose is used up (at point “a”) the lac operon gets turned “on.” Because it takes some time to generate enough lactose-digesting enzymes for the bacteria to have enough energy and matter to resume growth, there’s a lag phase (at “b”) Once those enzymes are produced (point “c”), growth can resume, and it continues until all of the lactose is consumed, causing another lag in growth (at “d.”).
[/qdeck]
4. Tackle these quizzes
4.1. lac Operon: Labeled Diagrams
[qwiz]
[h]Lac Operon: Interactive Diagrams
[i] Biohaiku
Operon System
Controls expression of genes
Such efficiency!
[q labels = “top”]
[l]operator
[fx] No. Please try again.
[f*] Correct!
[l]promoter
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]regulatory gene
[fx] No. Please try again.
[f*] Great!
[l]regulatory mRNA
[fx] No. Please try again.
[f*] Correct!
[l]regulatory protein
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]RNA polymerase
[fx] No. Please try again.
[f*] Correct!
[l]structural genes
[fx] No. Please try again.
[f*] Excellent!
[q labels = “top”]
[l]operator
[fx] No. Please try again.
[f*] Good!
[l]promoter
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]regulatory gene
[fx] No. Please try again.
[f*] Excellent!
[l]regulatory mRNA
[fx] No, that’s not correct. Please try again.
[f*] Excellent!
[l]regulatory protein
[fx] No, that’s not correct. Please try again.
[f*] Excellent!
[l]RNA polymerase
[fx] No. Please try again.
[f*] Excellent!
[l]structural genes
[fx] No, that’s not correct. Please try again.
[f*] Great!
[l]lactose
[fx] No. Please try again.
[f*] Correct!
[l]lactose-digesting enzymes
[fx] No, that’s not correct. Please try again.
[f*] Great!
[l]mRNA for lactose-digesting enzymes
[fx] No. Please try again.
[f*] Excellent!
[x][restart]
[/qwiz]
4.2. trp operon labeled diagrams
[qwiz]
[h]Trp operon: Labeled Diagrams
[i]
[q labels = “top”]
[l]enzymes for tryptophan synthesis
[fx] No, that’s not correct. Please try again.
[f*] Correct!
[l]mRNA for structural genes
[fx] No. Please try again.
[f*] Good!
[l]operator
[fx] No. Please try again.
[f*] Good!
[l]promoter
[fx] No. Please try again.
[f*] Great!
[l]regulatory gene
[fx] No. Please try again.
[f*] Good!
[l]regulatory protein
[fx] No. Please try again.
[f*] Good!
[l]mRNA for regulatory protein
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]RNA polymerase
[fx] No. Please try again.
[f*] Good!
[l]structural genes
[fx] No. Please try again.
[f*] Good!
[q labels = “top”]
[l]operator
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]promoter
[fx] No, that’s not correct. Please try again.
[f*] Correct!
[l]regulatory gene
[fx] No. Please try again.
[f*] Correct!
[l]regulatory gene’s mRNA
[fx] No. Please try again.
[f*] Great!
[l]regulatory protein
[fx] No. Please try again.
[f*] Good!
[l]RNA polymerase
[fx] No, that’s not correct. Please try again.
[f*] Good!
[l]structural genes
[fx] No. Please try again.
[f*] Excellent!
[l]tryptophan
[fx] No. Please try again.
[f*] Good!
[/qwiz]
4.3. Operons Quiz
[qwiz style=”width: 600px !important; min-height: 450px !important;” random=”true”]
[h] Operons
[i] Operons Biohaiku
An operator
When blocked by a repressor
Prevents transcription
[q json=”true” dataset_id=”Operons|1d4690ab006f00″ question_number=”1″] Which number is the regulatory gene?
[textentry single_char=”true”]
[c]ID E=[Qq]
[f]IFllcy4g4oCcMeKAnSBpcyB0aGUgcmVndWxhdG9yecKgZ2VuZS4=[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBUaGUgcmVndWxhdG9yeSBnZW5lIGNvZGVzIGZvciBhIHJlZ3VsYXRvcnkgcHJvdGVpbiwgd2hpY2ggY2FuLCBpbiB0dXJuLCBiaW5kIHdpdGggYSByZWdpb24gb24gdGhlIEROQSBjYWxsZWQgYW4gb3BlcmF0b3IuIFNvLCBmaW5kIHNvbWV0aGluZyB0aGF0IHJlcHJlc2VudHMgc29tZXRoaW5nIHRoYXQgY291bGQgYmluZCB3aXRoIHRoZSBETkEsIHRoZW4gdXNlIHRoZSBhcnJvd3MgaW4gdGhlIGRpYWdyYW0gdG8gZmluZCB0aGUgRE5BIHRoYXQgY29kZXMgZm9yIHRoYXQgaXQu
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d463f2d604300″ question_number=”2″] Which number is the regulatory mRNA?
[textentry single_char=”true”]
[c]ID I=[Qq]
[f]IFllcy4g4oCcMuKAnSBpcyB0aGUgcmVndWxhdG9yeSBtUk5BLg==[Qq]
[c]ICo=[Qq]
[f]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
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d45eb5bb43300″ question_number=”3″] Which number is the regulatory protein?
[textentry single_char=”true”]
[c]ID M=[Qq]
[f]IFllcy4g4oCcM+KAnSBpcyB0aGUgcmVndWxhdG9yeSBwcm90ZWluLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBSZW1lbWJlciB0aGUgY2VudHJhbCBkb2dtYSB0aGF0IEROQSBtYWtlcyBSTkEgbWFrZXMgcHJvdGVpbi4gWW91IGNhbiBzZWUgdGhpcyBwcm9jZXNzIHJlcHJlc2VudGVkIG9uIHRoZSBsZWZ0IHNpZGUgb2YgdGhlIGRpYWdyYW0uIFRoZSBwcm90ZWluIHdvdWxkIGJlIGF0IHRoZSBlbmQgb2YgdGhpcyBjaGFpbiBvZiBldmVudHMuIEluIGFkZGl0aW9uLCB0aGlzIHByb3RlaW4gY2FuIGJpbmQgd2l0aCB0aGUgRE5BIGF0IGEgcmVnaW9uIGNhbGxlZCB0aGUgb3BlcmF0b3IuIFVzZSB0aGVzZSBjbHVlcyB0byBmaW5kIHRoZSBhbnN3ZXIgbmV4dCB0aW1lLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d45a32e439700″ question_number=”4″] Which number is RNA polymerase?
[textentry single_char=”true”]
[c]ID Q=[Qq]
[f]IFllcy4g4oCcNOKAnSBpcyBSTkEgcG9seW1lcmFzZS4=[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBSTkEgcG9seW1lcmFzZSBpcyBhIHByb3RlaW4gdGhhdCB0cmFuc2NyaWJlcyBETkEgaW50byBtUk5BLiBJZiAmIzgyMjA7N2EmIzgyMjE7IHRocm91Z2ggJiM4MjIwOzdjJiM4MjIxOyByZXByZXNlbnQgdGhpcyBvcGVyb24mIzgyMTc7cyBzdHJ1Y3R1cmFsIGdlbmVzLCBhbmQgOSByZXByZXNlbnRzIG1STkEsIHdoYXQmIzgyMTc7cyB0aGUgb25seSB0aGluZyBpbiB0aGlzIGRpYWdyYW0gdGhhdCBjb3VsZCBiZSB0cmFuc2NyaWJpbmcgdGhlIGZvcm1lciBpbnRvIHRoZSBsYXR0ZXI/
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d455d54dedf00″ question_number=”5″] Which number is the promoter?
[textentry single_char=”true”]
[c]ID U=[Qq]
[f]IFllcy4g4oCcNeKAnSBpc8KgdGhlIHByb21vdGVyLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LsKgVGhlIHByb21vdGVyIGlzIHRoZSByZWdpb24gd2hlcmUgUk5BIHBvbHltZXJhc2UgYmluZHMgdG8gYmVnaW4gdHJhbnNjcmlwdGlvbiBvZiB0aGUgb3Blcm9uJiM4MjE3O3Mgc3RydWN0dXJhbCBnZW5lcy4gSWYgUk5BIHBvbHltZXJhc2UgaXMgJiM4MjIwOzQsJiM4MjIxOyB0aGVuIHdoYXQgaGFzIHRvIGJlIHRoZSBwcm9tb3Rlcj8=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d4512d3625f00″ question_number=”6″] Which number is the operator?
[textentry single_char=”true”]
[c]ID Y=[Qq]
[f]IFllcy4g4oCcNuKAnSBpc8KgdGhlIG9wZXJhdG9yLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBUaGUgb3BlcmF0b3IgaXMganVzdCAmIzgyMjA7ZG93bnN0cmVhbSYjODIyMTsgb2YgdGhlIHByb21vdGVyIGFuZCBqdXN0ICYjODIyMDt1cHN0cmVhbSYjODIyMTsgb2YgdGhlIHN0cnVjdHVyYWwgZ2VuZXMuIElmIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzIGFyZSBhdCA3YSB0aHJvdWdoIDdjLCBhbmQgdGhlIHByb21vdGVyIGlzIGF0ICYjODIyMDs0LCYjODIyMTsgdGhlbiB3aGljaCBudW1iZXIgaXMgcmVwcmVzZW50aW5nIHRoZSBvcGVyYXRvcj8=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d44c851e5df00″ question_number=”7″ multiple_choice=”true”] Which of the following would represent one of the structural genes?
[c]IDE=[Qq]
[f]IE5vLiAmIzgyMjA7MSYjODIyMTsgcmVwcmVzZW50cyBhIHJlZ3VsYXRvcnkgZ2VuZS4=[Qq]
[c]IDU=[Qq]
[f]IE5vLiAmIzgyMjA7NSYjODIyMTsgcmVwcmVzZW50cyB0aGUgcHJvbW90ZXIu[Qq]
[c]IDY=[Qq]
[f]IE5vLiAmIzgyMjA7NiYjODIyMTsgcmVwcmVzZW50cyB0aGUgb3BlcmF0b3Iu[Qq]
[c]ID di[Qq]
[f]IFllcy4gJiM4MjIwOzdiJiM4MjIxOyBpcyBvbmUgb2YgdGhyZWUgc3RydWN0dXJhbCBnZW5lcyBpbiB0aGUgbGFjIG9wZXJvbi4gRWFjaCBvZiB0aGVzZSBnZW5lcyBnZXRzIHRyYW5zY3JpYmVkIGludG8gbVJOQSwgYW5kIHRoZW4gc3ludGhlc2l6ZWQgaW50byBvbmUgb2YgdGhlIHRocmVlIHByb3RlaW5zIHRoYXQgYnJlYWsgZG93biBsYWN0b3NlIGludG8gZ2x1Y29zZSBhbmQgZ2FsYWN0b3NlLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d447dd0695f00″ question_number=”8″] Which number represents lactose?
[textentry single_char=”true”]
[c]ID g=[Qq]
[f]IFllcy4g4oCcOOKAnSBpcyBsYWN0b3NlLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlIGFyZSB0d28gaGludHMuIDEpIExhY3Rvc2UgaXMgYSBkaXNhY2NoYXJpZGUsIGEgc3VnYXIgbWFkZSBvZiB0d28gc2ltcGxlIHN1Z2FyIChtb25vc2FjY2hhcmlkZSkgc3VidW5pdHMuIFdoYXQgb24gdGhpcyBkaWFncmFtIGNvdWxkIGJlIG1hZGUgb2YgdHdvIHN1YnVuaXRzPyDCoDIpIExhY3Rvc2UgYmluZHMgd2l0aCB0aGUgcmVndWxhdG9yeSBwcm90ZWluLCB3aGljaCB0dXJucyB0aGUgb3Blcm9uICYjODIyMDtvZmYuJiM4MjIxOyBJZiAmIzgyMjA7MyYjODIyMTsgaXMgdGhlIHJlZ3VsYXRvcnkgcHJvdGVpbiwgdGhlbiB3aGF0IGNvdWxkIGJlIHNvbWV0aGluZyB0aGF0IGJpbmRzIHdpdGggdGhpcyBwcm90ZWluPw==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d4435a2f8c300″ question_number=”9″] Which number represents the mRNA that’s transcribed from the structural genes in this operon?
[textentry single_char=”true”]
[c]ID k=[Qq]
[f]IFllcy4g4oCcOeKAnSBpcyB0aGUgbVJOQSB0aGF0IGNvZGVzIGZvciB0aGUgb3Blcm9uJiM4MjE3O3Mgc3RydWN0dXJhbCBnZW5lcy4=[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBJZiB0aGUgdGhyZWUgYm94ZXMgYXQgMTAgcmVwcmVzZW50ZWQgdGhlIGdlbmUgcHJvZHVjdHMsIGFuZCB0aGUgdGhyZWUgZ2VuZXMgYXQgJiM4MjIwOzcmIzgyMjE7IHJlcHJlc2VudCB0aGUgc3RydWN0dXJhbCBnZW5lcywgdGhlbiB3aGF0IGhhcyB0byBiZSB0aGUgbVJOQSBmb3IgdGhlc2UgZ2VuZXM/
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d43eb217c4300″ question_number=”10″ multiple_choice=”true”] Which of the following would best describe the operon shown below?
[c]IGluZHVjaWJsZc KgIMKgIMKgIA==[Qq][c]IHJlcHJlc3NpYmxl
Cg==[Qq][f]IFllcy4gVGhlIG9wZXJvbiBzaG93biBhYm92ZSBpcyAmIzgyMjA7aW5kdWNpYmxlLiYjODIyMTsgVG8gJiM4MjIwO2luZHVjZSYjODIyMTsgaXMgdG8gY2F1c2Ugc29tZXRoaW5nIHRvIGhhcHBlbi4gVGhlIGxhYyBvcGVyb24gaXMgaW5kdWNpYmxlIGJlY2F1c2UgbGFjdG9zZSwgd2hlbiBwcmVzZW50LCB0dXJucyB0aGUgb3Blcm9uICYjODIyMDtvbi4mIzgyMjE7IFRoZSBkZWZhdWx0IGNvbmRpdGlvbiwgd2hlbiBsYWN0b3NlIGlzIGFic2VudCwgaXMgZm9yIHRoaXMgb3Blcm9uIHN5c3RlbSB0byBiZSB0dXJuZWQgJiM4MjIwO29mZi4mIzgyMjE7[Qq]
[f]IE5vLiBUaGUgb3Blcm9uIHNob3duIGFib3ZlIGlzICYjODIyMDtpbmR1Y2libGUuJiM4MjIxOyBUbyAmIzgyMjA7aW5kdWNlJiM4MjIxOyBpcyB0byBjYXVzZSBzb21ldGhpbmcgdG8gaGFwcGVuLiBUaGUgbGFjIG9wZXJvbiBpcyBpbmR1Y2libGUgYmVjYXVzZSBsYWN0b3NlLCB3aGVuIHByZXNlbnQsIHR1cm5zIHRoZSBvcGVyb24gJiM4MjIwO29uLiYjODIyMTsgVGhlIGRlZmF1bHQgY29uZGl0aW9uLCB3aGVuIGxhY3Rvc2UgaXMgYWJzZW50LCBpcyBmb3IgdGhpcyBvcGVyb24gc3lzdGVtIHRvIGJlIHR1cm5lZCAmIzgyMjA7b2ZmLiYjODIyMTs=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d439e4bf3df00″ question_number=”11″ multiple_choice=”true”] The diagram below represents the lac operon. Which statement about the diagram below is most correct?
[c]IFRoZSBzdHJ1Y3R1cmFsIGdlbmVzIGFyZSBiZWluZyB0cmFuc2NyaWJlZCBpbnRvIGEgcHJvdGVpbiwgYXMgaXMgc2hvd24gYXQgJiM4MjIwOzEsJiM4MjIxOyAmIzgyMjA7MiwmIzgyMjE7IGFuZCAmIzgyMjA7My4mIzgyMjE7[Qq]
[f]IE5vLiBXaGF0JiM4MjE3O3Mgc2hvd24gYXQgJiM4MjIwOzEsJiM4MjIxOyAmIzgyMjA7MiwmIzgyMjE7IGFuZCAmIzgyMjA7MyYjODIyMTsgYXJlIHRoZSByZWd1bGF0b3J5IGdlbmUsIHRoZSBtUk5BIHRyYW5zY3JpYmVkIGZyb20gdGhpcyBnZW5lLCBhbmQgdGhlIHJlZ3VsYXRvcnkgcHJvdGVpbi4gVGhlIHN0cnVjdHVyYWwgZ2VuZXMgKGF0ICYjODIyMDs3JiM4MjIxOykgYXJlIGJsb2NrZWQgYmVjYXVzZSB0aGUgcmVndWxhdG9yeSBwcm90ZWluICgzKSBpcyBib3VuZCB0byB0aGUgb3BlcmF0b3IgKDYpLg==[Qq]
[c]IFRoZSBzdHJ1Y3R1cmFsIGdlbmVzIGFyZSBub3QgYmVpbmcgZXhwcmVzc2Vk IGJlY2F1c2UgbGFjdG9zZSBpcyBub3QgaW4gdGhlIGVudmlyb25tZW50Lg==[Qq]
[f]IFllcy4gQmVjYXVzZSBsYWN0b3NlIGlzIG5vdCBpbiB0aGUgZW52aXJvbm1lbnQsIHRoZSByZWd1bGF0b3J5IHByb3RlaW4gKDMpIGhhcyBhIGNvbmZvcm1hdGlvbiB0aGF0IGVuYWJsZXMgaXQgdG8gYmluZCB3aXRoIHRoZSBvcGVyYXRvciAoNiksIHByZXZlbnRpbmcgUk5BIHBvbHltZXJhc2UgZnJvbSB0cmFuc2NyaWJpbmcgdGhlIHN0cnVjdHVyYWwgZ2VuZXMu[Qq]
[c]IFRoZSBzdHJ1Y3R1cmFsIGdlbmVzIGFyZSBub3QgYmVpbmcgZXhwcmVzc2VkLCBiZWNhdXNlIFJOQSBwb2x5bWVyYXNlIGlzIGJsb2NraW5nIHRoZSByZWd1bGF0b3J5IHByb3RlaW4gZnJvbSB0cmFuc2NyaWJpbmcgdGhlIGdlbmVzLg==[Qq]
[f]IE5vIChidXQgeW91IGhhdmUgdGhlIHJpZ2h0IGlkZWEpLiBCZWNhdXNlIGxhY3Rvc2UgaXMgbm90IGluIHRoZSBlbnZpcm9ubWVudCwgdGhlIHJlZ3VsYXRvcnkgcHJvdGVpbiAoMykgaGFzIGEgY29uZm9ybWF0aW9uIHRoYXQgZW5hYmxlcyBpdCB0byBiaW5kIHdpdGggdGhlIG9wZXJhdG9yICg2KSwgcHJldmVudGluZyBSTkEgcG9seW1lcmFzZSBmcm9tIHRyYW5zY3JpYmluZyB0aGUgc3RydWN0dXJhbCBnZW5lcy4=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d42769a0dc300″ question_number=”15″] Which number represents the substrate of the enzymes produced by this operon?
[textentry single_char=”true”]
[c]ID g=[Qq]
[f]IFllcy4g4oCcOOKAnSBpcyBsYWN0b3NlLCB3aGljaCBpcyB0aGUgc3Vic3RyYXRlIG9mIHRoZSBlbnp5bWVzIHRoYXQgdGhpcyBvcGVyb24gcHJvZHVjZXMu[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYcKgaGludC7CoFRoZSBzdWJzdHJhdGUgb2YgdGhlIGVuenltZXMgcHJvZHVjZWQgYnkgdGhpcyBvcGVyb24gaXMgdGhlIHNhbWUgbW9sZWN1bGUgd2hvc2UgcHJlc2VuY2UgdHVybnMgdGhlIG9wZXJvbiAmIzgyMjA7b24uJiM4MjIxOyBXaGljaCBtb2xlY3VsZSBiaW5kcyB3aXRoIHRoZSByZWd1bGF0b3J5IHByb3RlaW4gKHNob3duIGF0ICYjODIyMDszJiM4MjQyOykgaW4gYSB3YXkgdGhhdCBjaGFuZ2VzIHRoYXQgcHJvdGVpbiYjODIxNztzIHNoYXBlLCBrZWVwaW5nIGl0IGZyb20gYmluZGluZyB3aXRoIHRoZSBvcGVyYXRvcj8=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d41e63f2c8b00″ question_number=”17″] The diagram below represents the trp operon. Which number is the regulatory mRNA?
[textentry single_char=”true”]
[c]ID I=[Qq]
[f]IFllcy4g4oCcMuKAnSBpcyB0aGUgcmVndWxhdG9yeSBtUk5BLg==[Qq]
[c]ICo=[Qq]
[f]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[Qq]
[q json=”true” dataset_id=”Operons|1d40b094ff1700″ question_number=”21″] The diagram below represents the trp operon. Which number is the operator?
[textentry single_char=”true”]
[c]ID Y=[Qq]
[f]IFllcy4g4oCcNuKAnSBpc8KgdGhlIG9wZXJhdG9yLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBUaGUgb3BlcmF0b3IgaXMganVzdCAmIzgyMjA7ZG93bnN0cmVhbSYjODIyMTsgb2YgdGhlIHByb21vdGVyIGFuZCBqdXN0ICYjODIyMDt1cHN0cmVhbSYjODIyMTsgb2YgdGhlIHN0cnVjdHVyYWwgZ2VuZXMuIElmIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzIGFyZSBhdCA3LCBhbmQgdGhlIHByb21vdGVyIGlzIGF0ICYjODIyMDs0LCYjODIyMTsgdGhlbiB3aGljaCBudW1iZXIgaXMgcmVwcmVzZW50aW5nIHRoZSBvcGVyYXRvcj8=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d4016e9ee4f00″ question_number=”23″] The diagram below represents the trp operon. Which number represents tryptophan?
[textentry single_char=”true”]
[c]ID g=[Qq]
[f]IFllcy4g4oCcOOKAnSBpcyB0cnlwdG9waGFuLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50OiB0cnlwdG9waGFuIGlzIHdoYXQmIzgyMTc7cyBzZWVuIGJpbmRpbmcgdG8gdGhlIHJlZ3VsYXRvcnkgcHJvdGVpbiAoJiM4MjIwOzMmIzgyNDM7KSwgY2hhbmdpbmcgaXRzIHNoYXBlIHNvIHRoYXQgaXQgY2FuIGJpbmQgdG8gdGhlIG9wZXJhdG9yIHJlZ2lvbiBvZiB0aGUgb3Blcm9uLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3f7aead1a300″ question_number=”25″] Shown below is a representation of the trp operon from the Biology Coloring Workbook. Which letter represents the operator region of the operon?
[textentry single_char=”true”]
[c]IE Q=[Qq]
[f]IFllcy4g4oCcRCYjODIyMTvCoGlzIHRoZSBvcGVyYXRvci4=[Qq]
[c]ICo=[Qq]
[f]IE5vLiBGaW5kIGEgbGV0dGVyIHRoYXQgcmVwcmVzZW50cyB0aGUgcGFydCBvZiB0aGUgb3Blcm9uJiM4MjE3O3MgRE5BIHRoYXQgdGhlIHJlcHJlc3NvciBwcm90ZWluIChKKSBjYW4gYmluZCB0bywgYmxvY2tpbmcgdHJhbnNjcmlwdGlvbi4=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3edeebb4f700″ question_number=”27″] Which number represents this operon’s co-repressor?
[textentry single_char=”true”]
[c]ID g=[Qq]
[f]IFllcy4g4oCcOOKAnSBpcyB0aGUgY28tcmVwcmVzc29yLCB0cnlwdG9waGFuLiBJdCYjODIxNztzIGNhbGxlZCBhIGNvLXJlcHJlc3NvciBiZWNhdXNlIGl0IHdvcmtzIHdpdGggdGhlIHJlcHJlc3NvciAoJiM4MjIwOzMmIzgyMjE7KSB0byBiaW5kIHdpdGggdGhlIG9wZXJhdG9yIHRvIHNodXQgZG93biB0aGUgdHJhbnNjcmlwdGlvbiBvZiB0aGUgc3RydWN0dXJhbCBnZW5lcy4=[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50OiB0aGUgY28tcmVwcmVzc29ywqBpcyB3aGF0JiM4MjE3O3Mgc2VlbiBiaW5kaW5nIHRvIHRoZSByZWd1bGF0b3J5IHByb3RlaW4gKCYjODIyMDszJiM4MjQzOyksIGNoYW5naW5nIGl0cyBzaGFwZSBzbyB0aGF0IGl0IGNhbiBiaW5kIHRvIHRoZSBvcGVyYXRvciByZWdpb24gb2YgdGhlIG9wZXJvbi4gSW4gb3RoZXIgd29yZHMsIHlvdSYjODIxNztyZSBsb29raW5nIGZvciB0cnlwdG9waGFuLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3e8d6e14cb00″ question_number=”28″ multiple_choice=”true”] In the lac operon system
[c]IFJlcHJlc3NvciBwcm90ZWlucyBtYXkgYmluZCB0byB0aGUgb3BlcmF0b3IgcmVnaW9u LCBibG9ja2luZyB0cmFuc2NyaXB0aW9uIG9mIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzLg==[Qq]
[f]IENvcnJlY3QuIEluIHRoZSBsYWMgb3Blcm9uLCB3aGVuIHJlcHJlc3NvciBwcm90ZWlucyBhcmUgYm91bmQgdG8gdGhlIG9wZXJhdG9yLCB0aGUgc3RydWN0dXJhbCBnZW5lcyBjYW5ub3QgYmUgdHJhbnNjcmliZWQu[Qq]
[c]IHN0cnVjdHVyYWwgZ2VuZXMgbWFrZSBhIHJlcHJlc3NvciBwcm90ZWluIHRoYXQgYmluZCB0byB0aGUgcHJvbW90ZXIsIHByZXZlbnRpbmcgdHJhbnNjcmlwdGlvbi4=[Qq]
[f]IE5vLiBUaGUgc3RydWN0dXJhbCBnZW5lcyBtYWtlIHRoZSBlbnp5bWVzIGZvciBkaWdlc3RpbmcgbGFjdG9zZS4=[Qq]
[c]IGxhY3Rvc2UgdHVybnMgdGhlIG9wZXJvbiBvZmY=[Qq]
[f]IE5vLiBJbiB0aGUgbGFjIG9wZXJvbiwgbGFjdG9zZSB0dXJucyB0aGUgb3Blcm9uICYjODIyMDtvbi4mIzgyMjE7IEluIG90aGVyIHdvcmRzLCB0aGUgcnVsZSBpcyAmIzgyMjA7b25seSBtYWtlIHRoZSBlbnp5bWVzIGZvciBsYWN0b3NlIGRpZ2VzdGlvbiB3aGVuIGxhY3Rvc2UgaXMgaW4gdGhlIGVudmlyb25tZW50LiYjODIyMTs=[Qq]
[c]IHJpYm9zb21lcyBjYW5ub3QgcGFzcyBieSB0aGUgcmVwcmVzc29yIHByb3RlaW4gYm91bmQgdG8gdGhlIG9wZXJhdG9yIHJlZ2lvbg==[Qq]
[f]IE5vLiBJdCYjODIxNztzIFJOQSBwb2x5bWVyYXNlIChub3Qgcmlib3NvbWVzKSB0aGF0IGNhbiYjODIxNzt0IHBhc3MgYnkgdGhlIHJlcHJlc3NvciBwcm90ZWluIGJvdW5kIHRvIHRoZSBvcGVyYXRvciByZWdpb24u
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3e2950157f00″ question_number=”29″ multiple_choice=”true”] In an operon, active repressor molecules have an effect when they bind to:
[c]IFByb21vdGVycw==[Qq]
[f]IE5vLiBSTkEgcG9seW1lcmFzZSBpcyB3aGF0IGJpbmRzIHRvIHRoZSBwcm9tb3Rlci4gVGhpcyBxdWVzdGlvbiBpcyBhc2tpbmcgeW91IHdoYXQgcGFydCBvZiB0aGUgb3Blcm9uIHN5c3RlbSByZXByZXNzb3IgbW9sZWN1bGVzIGJpbmQgdG8uIExvb2sgY2xvc2VseSBhdCB0aGUgd29yZCAmIzgyMjA7b3Blcm9uJiM4MjIxOyBmb3IgYSBjbHVlLg==[Qq]
[c]IFJpYm9zb21lcw==[Qq]
[f]IE5vLiBSaWJvc29tZXMgZG9uJiM4MjE3O3QgcGxheSBhbnkgcm9sZSBhcyByZXByZXNzb3JzIHdpdGhpbiBvcGVyb25zICh0aG91Z2ggdGhleSBkbyB0cmFuc2xhdGUgdGhlIHJlZ3VsYXRvcnkgYW5kIHN0cnVjdHVyYWwgUk5BKS7CoFRoaXMgcXVlc3Rpb24gaXMgYXNraW5nIHlvdSB3aGF0IHBhcnQgb2YgdGhlIG9wZXJvbiBzeXN0ZW0gcmVwcmVzc29yIG1vbGVjdWxlcyBiaW5kIHRvLiBMb29rIGNsb3NlbHkgYXQgdGhlIHdvcmQgJiM4MjIwO29wZXJvbiYjODIyMTsgZm9yIGEgY2x1ZS4=[Qq]
[c]IFN0cnVjdHVyYWwgZ2VuZXM=[Qq]
[f]IE5vLiBSZXByZXNzb3IgbW9sZWN1bGVzIGJsb2NrIHRyYW5zY3JpcHRpb24gb2YgdGhlIHN0cnVjdHVyYWwgZ2VuZXMsIGJ1dCBub3QgYnkgZGlyZWN0bHkgYmluZGluZyB0byB0aGVtLsKgTG9vayBjbG9zZWx5IGF0IHRoZSB3b3JkICYjODIyMDtvcGVyb24mIzgyMjE7IGZvciBhIGNsdWUu[Qq]
[c]IFJOQSBwb2x5bWVyYXNl[Qq]
[f]IE5vLiBUaGUgcmVwcmVzc29yIG1vbGVjdWxlcyBibG9jayBSTkEgcG9seW1lcmFzZSwgYnV0IHRoZXkgZG9uJiM4MjE3O3QgYmluZCB0byBpdC7CoFRoaXMgcXVlc3Rpb24gaXMgYXNraW5nIHlvdSB3aGF0IHBhcnQgb2YgdGhlIG9wZXJvbiBzeXN0ZW0gcmVwcmVzc29yIG1vbGVjdWxlcyBiaW5kIHRvLiBMb29rIGNsb3NlbHkgYXQgdGhlIHdvcmQgJiM4MjIwO29wZXJvbiYjODIyMTsgZm9yIGEgY2x1ZS4=[Qq]
[c]IE9wZXJh dG9ycw==[Qq]
[f]IFllcyEgSW4gYW4gb3Blcm9uLCByZXByZXNzb3IgbW9sZWN1bGVzIGhhdmUgYW4gZWZmZWN0IHdoZW4gdGhleSBiaW5kIHRvIG9wZXJhdG9ycy4=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3dd0d651a700″ question_number=”30″ multiple_choice=”true”] The lac operon system is an important adaptation for E. coli bacteria because the sugar lactose:
[c]IElzIHJlcXVpcmVkIGZvciB0aGUgcHJvZHVjdGlvbiBvZiB0aGUgc3RydWN0dXJhbCBnZW5lcyB0aGF0IGNyZWF0ZSB0aGUgcmVwcmVzc29yIHByb3RlaW5zIHVwb24gd2hpY2ggdGhpcyBvcGVyb24gZGVwZW5kcy4=[Qq]
[f]IE5vLiBGaXJzdCwgbGFjdG9zZSBpcyB0aGUgc3Vic3RyYXRlIG9mIHRoZSBlbnp5bWVzIHByb2R1Y2VkIGJ5IHRoZSBsYWMgb3Blcm9uIHN5c3RlbTogaXQmIzgyMTc7cyBub3QgcHJvZHVjZWQgYnkgdGhlIHN5c3RlbS4gU2Vjb25kLCBpdCYjODIxNztzIG5vdCBwYXJ0IG9mIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzICh3aGljaCBhcmUgbWFkZSBvZiBETkEpLg==[Qq]
[c]IElzIHRoZSBvbmx5IHN1Z2FyIHRoYXQgRS4gY29sacKgY2FuIHVzZQ==[Qq]
[f]IE5vLiBFLiBjb2xpwqBjYW4gbWV0YWJvbGl6ZSBvdGhlciBzdWdhcnMgYXMgd2VsbCwgbm90YWJseSBnbHVjb3NlLg==[Qq]
[c]IElzIG9ubHnCoGF2YWlsYWJsZSBzb21ldGltZXM7IG1ha2luZyBsYWN0b3NlLWRpZ2VzdG luZyBlbnp5bWVzIGNvbnRpbnVvdXNseSB3b3VsZCBiZSBhIHdhc3RlIG9mIGVuZXJneQ==[Qq]
[f]IFllcy4gTGFjdG9zZSBpcyBvbmx5IHBlcmlvZGljYWxseSBhdmFpbGFibGUgdG8gRS4gY29saSwgc28gaXQgb25seSBtYWtlcyBzZW5zZSBmb3IgdGhlc2UgYmFjdGVyaWEgdG8gc3ludGhlc2l6ZSB0aGUgZW56eW1lcyBmb3IgZGlnZXN0aW5nIGxhY3Rvc2Ugd2hlbiBpdCYjODIxNztzIGF2YWlsYWJsZSBpbiB0aGUgZW52aXJvbm1lbnQu[Qq]
[c]IEFjdHMgdG8gdHVybiBvZmYgdGhlIHN5c3RlbQ==[Qq]
[f]IE5vLiBJbiB0aGUgTGFjIG9wZXJvbiBzeXN0ZW0sIHRoZSBwcmVzZW5jZSBvZiBsYWN0b3NlIHR1cm5zIHRoZSBzeXN0ZW0gb24uIEluIHRoZSBwcmVzZW5jZSBvZiBsYWN0b3NlLCB0aGUgc3RydWN0dXJhbCBnZW5lcyB0aGF0IGNvZGUgZm9yIGxhY3Rvc2UtZGlnZXN0aW5nIGVuenltZXMgYXJlIHRyYW5zY3JpYmVkIGFuZCB0cmFuc2xhdGVkIHNvIHRoYXQgRS4gY29saSBjYW4gZGlnZXN0IHRoaXMgZW5lcmd5IHNvdXJjZS4=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3d7d04a59700″ question_number=”31″ multiple_choice=”true”] The structural genes in the lac operon system are only transcribed when
[c]IExhY3Rvc2UgaXMgYWJzZW50[Qq]
[f]IE5vLiBJbiB0aGUgbGFjIG9wZXJvbiwgdGhlIHN0cnVjdHVyYWwgZ2VuZXMgYXJlIHRyYW5zY3JpYmVkIHdoZW4gbGFjdG9zZSBpcyBwcmVzZW50Lg==[Qq]
[c]IFRoZSByZXByZXNzb3IgcHJvdGVpbiBpcyBhdHRhY2hlZCB0byB0aGUgb3BlcmF0b3IgZ2VuZQ==[Qq]
[f]IE5vLiBXaGVuIHRoZSByZXByZXNzb3IgcHJvdGVpbiBpcyBhdHRhY2hlZCB0byB0aGUgb3BlcmF0b3IgZ2VuZSwgdGhlIFJOQSBwb2x5bWVyYXNlIGlzIGJsb2NrZWQgYW5kIGNhbiYjODIxNzt0IHRyYW5zY3JpYmUgdGhlIHN0cnVjdHVyYWwgZ2VuZXMu[Qq]
[c]IExhY3Rvc2UgYmluZHMgdG8gdGhlIFJOQSBwb2x5bWVyYXNl[Qq]
[f]IE5vLiBUaGUgbGFjIG9wZXJvbiBzeXN0ZW0gd29ya3MgdGhyb3VnaCB0aGUgcmVwcmVzc29yIHByb3RlaW4gYmluZGluZyB0byB0aGUgb3BlcmF0b3IgcmVnaW9uLCB3aGljaCBibG9ja3MgUk5BIHBvbHltZXJhc2UgZnJvbSB0cmFuc2NyaWJpbmcgdGhlIHN0cnVjdHVyYWwgZ2VuZXMuIE5vdGhpbmcgaW4gdGhpcyBzeXN0ZW0gYmluZHMgZGlyZWN0bHkgdG8gUk5BIHBvbHltZXJhc2Uu[Qq]
[c]IExhY3Rvc2UgYmluZHMgd2l0aCB0 aGUgcmVwcmVzc29yIHByb3RlaW4=[Qq]
[f]IEV4Y2VsbGVudC4gSW4gdGhlIGxhYyBvcGVyb24gc3lzdGVtLCB0aGUgc3RydWN0dXJhbCBnZW5lcyBhcmUgb25seSB0cmFuc2NyaWJlZCB3aGVuIGxhY3Rvc2UgYmluZHMgdG8gdGhlIHJlcHJlc3NvciBwcm90ZWluLiBUaGlzIGNhdXNlcyBhbiBhbGxvc3RlcmljIGNoYW5nZSBpbiB0aGUgc2hhcGUgb2YgdGhlIHJlcHJlc3NvciBwcm90ZWluIHNvIHRoYXQgaXQgY2FuIG5vIGxvbmdlciBiaW5kIHRvIHRoZSBvcGVyYXRvciByZWdpb24sIGFsbG93aW5nIHRyYW5zY3JpcHRpb24gb2YgdGhlIHN0cnVjdHVyYWwgZ2VuZXMgdG8gb2NjdXIu[Qq]
[c]IEJhY3RlcmlhIG1ha2UgbGFjdG9zZQ==[Qq]
[f]IE5vLiBUaGUgbGFjIG9wZXJvbiBpcyBhYm91dCBob3cgYmFjdGVyaWEgZGlnZXN0IGxhY3Rvc2UuIE1hbW1hbHMgKGxpa2UgcGVvcGxlLCBjb3dzLCB3aGFsZXMsIGFuZCBiYXRzKSBtYWtlIGxhY3Rvc2Ugd2hlbiB0aGV5IG1ha2UgbWlsay4=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3d2932f98700″ question_number=”32″ multiple_choice=”true”] In the lac operon system in E. coli, the repressor molecules are:
[c]IExhY3Rvc2Ugc3VnYXJz[Qq]
[f]IE5vLiBMYWN0b3NlIHN1Z2FycyBhcmUgdGhlIHN1YnN0cmF0ZSBvZiB0aGUgZW56eW1lcyBwcm9kdWNlZCBieSB0aGUgc3RydWN0dXJhbCBnZW5lcy4gV2hhdCBraW5kIG9mIG1vbGVjdWxlIGNvdWxkIGJsb2NrIHRoZSB0cmFuc2NyaXB0aW9uIG9mIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzPw==[Qq]
[c]IFByb3 RlaW5z[Qq]
[f]IFllcyEgVGhlIHJlcHJlc3NvciBtb2xlY3VsZXMgYXJlIHByb3RlaW5zIHByb2R1Y2VkIGJ5IHRyYW5zY3JpcHRpb24gYW5kIHRyYW5zbGF0aW9uIG9mIHRoZSBvcGVyb24mIzgyMTc7cyByZWd1bGF0b3J5IGdlbmVzLg==[Qq]
[c]IFNob3J0IHBpZWNlcyBvZiBETkE=[Qq]
[f]IE5vLiBUaGUgcmVwcmVzc29yIG1vbGVjdWxlcyBpbiB0aGXCoGxhYyBvcGVyb24gc3lzdGVtIGFyZSBjYXBhYmxlIG9mIGJpbmRpbmcgdG8gRE5BIGFuZCBibG9ja2luZyB0cmFuc2NyaXB0aW9uIG9mIHRoZSBvcGVyb24mIzgyMTc7cyBzdHJ1Y3R1cmFsIGdlbmVzIChidXQgdGhleSYjODIxNztyZSBub3QgbWFkZSBvZiBETkEpLiBXaGF0wqBraW5kIG9mIHJlZ3VsYXRvcnkgbW9sZWN1bGUgY291bGQgYmluZCB0byBETkEgaW4gdGhpcyB3YXk/[Qq]
[c]IEJvdW5kIHRvIHRoZSBwcm9tb3RvciByZWdpb24=[Qq]
[f]IE5vLCBUaGUgcmVwcmVzc29yIG1vbGVjdWxlcyBpbiB0aGXCoGxhYyBvcGVyb24gc3lzdGVtIGJpbmQgdG8gdGhlIG9wZXJhdG9yIHJlZ2lvbiwgd2hpY2ggaXMganVzdCBkb3duc3RyZWFtIG9mIHRoZSBwcm9tb3Rlci4gV2hhdCBraW5kIG9mIG1vbGVjdWxlcyBjb3VsZCBhIGNlbGwgcHJvZHVjZSB0aGF0IGNvdWxkIGJpbmQgdG8gRE5BIGluIHRoaXMgd2F5Pw==[Qq]
[c]IFByb2R1Y2VkIGJ5IGEgc3RydWN0dXJhbCBnZW5l[Qq]
[f]IE5vLsKgVGhlIHJlcHJlc3NvciBtb2xlY3VsZXMgaW4gdGhlIGxhYyBvcGVyb24gc3lzdGVtIGFyZSBwcm9kdWNlZCBieSB0cmFuc2NyaXB0aW9uIGFuZCB0cmFuc2xhdGlvbiBvZiB0aGUgcmVndWxhdG9yeSBnZW5lLiBXaGF0IGtpbmQgb2YgbW9sZWN1bGVzIGFyZSB0aGUgcHJvZHVjdCBvZiB0cmFuc2NyaXB0aW9uIGFuZCB0cmFuc2xhdGlvbj8=
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3cce6529cb00″ question_number=”33″ multiple_choice=”true”] In the lac operon system, the presence of lactose causes E. coli cells to produce a series of enzymes that break lactose apart into two monosaccharides that can then be further metabolized for matter and energy. When E. coli runs out of lactose:
[c]IHRoZSByZXByZXNzb3IgcHJvdGVpbiBiaW5kcyB0byB0aGUgcHJvbW90ZXIgcmVnaW9u[Qq]
[f]IE5vLiBJbiB0aGUgbGFjIG9wZXJvbiBzeXN0ZW0sIHdoZW4gRS4gY29saSBydW5zIG91dCBvZiBsYWN0b3NlLCB0aGUgcmVwcmVzc29yIHByb3RlaW4gYXNzdW1lcyBhIHNoYXBlIHRoYXQgZW5hYmxlcyBpdCB0byBiaW5kIHdpdGggdGhlIG9wZXJhdG9yIHJlZ2lvbiAobm90IHRoZSBwcm9tb3Rlciku[Qq]
[c]IHRoZSByZXByZXNzb3IgcHJvdGVpbiBiaW 5kcyB0byB0aGUgb3BlcmF0b3IgcmVnaW9u[Qq]
[f]IFllcy7CoEluIHRoZSBsYWMgb3Blcm9uIHN5c3RlbSwgd2hlbiBFLiBjb2xpIHJ1bnMgb3V0IG9mIGxhY3Rvc2UsIHRoZSByZXByZXNzb3IgcHJvdGVpbiBhc3N1bWVzIGEgc2hhcGUgdGhhdCBlbmFibGVzIGl0IHRvIGJpbmQgd2l0aCB0aGUgb3BlcmF0b3IgcmVnaW9uLCBwcmV2ZW50aW5nIFJOQSBwb2x5bWVyYXNlIGZyb20gdHJhbnNjcmliaW5nIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzLg==[Qq]
[c]IFJOQSBwb2x5bWVyYXNlIGF0dGFjaGVzIHRvIHRoZSByZXByZXNzb3IgcmVnaW9u[Qq]
[f]IE5vLiBPcGVyb25zIGhhdmUgb3BlcmF0b3IgcmVnaW9ucywgbm90IHJlcHJlc3NvciByZWdpb25zLiDCoEluIHRoZSBsYWMgb3Blcm9uIHN5c3RlbSwgd2hlbiBFLiBjb2xpIHJ1bnMgb3V0IG9mIGxhY3Rvc2UsIHRoZSByZXByZXNzb3IgcHJvdGVpbiBhc3N1bWVzIGEgc2hhcGUgdGhhdCBlbmFibGVzIGl0IHRvIGJpbmQgd2l0aCB0aGUgb3BlcmF0b3IsIHdoaWNoIGJsb2NrcyBSTkEgcG9seW1lcmFzZSBmcm9tIHRyYW5zY3JpYmluZyB0aGUgc3RydWN0dXJhbCBnZW5lcy4=[Qq]
[c]IFJOQSBwb2x5bWVyYXNlIGFsbG93cyB0aGUgc3RydWN0dXJhbCBnZW5lcyB0byBtYWtlIG1STkE=[Qq]
[f]IE5vLiBJdCYjODIxNztzIHRoZSBvcHBvc2l0ZS4gSW4gdGhlIGxhYyBvcGVyb24gc3lzdGVtLCB3aGVuIEUuIGNvbGkgcnVucyBvdXQgb2YgbGFjdG9zZSwgdGhlIHJlcHJlc3NvciBwcm90ZWluIGFzc3VtZXMgYSBzaGFwZSB0aGF0IGVuYWJsZXMgaXQgdG8gYmluZCB3aXRoIHRoZSBvcGVyYXRvciwgd2hpY2ggYmxvY2tzIFJOQSBwb2x5bWVyYXNlIGZyb20gdHJhbnNjcmliaW5nIHRoZSBzdHJ1Y3R1cmFsIGdlbmVzLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3c7a937dbb00″ question_number=”34″ multiple_choice=”true”] The trp operon system is an important adaptation for E. coli bacteria because the amino acid tryptophan
[c]IGlzIHBhcnRpY3VsYXJseSBpbXBvcnRhbnQgZm9yIA==RS4gY29saSYjODIxNztzwqBtZXRhYm9saXNtIChtdWNoIG1vcmUgc28sIGZvciBleGFtcGxlLCB0aGFuIHRoZSBhbWlubyBhY2lkcyBhcmdpbmluZSBvciBhc3BhcmFnaW5lKS4=[Qq]
[f]IE5vLsKgRS4gY29saQ==IGNlcnRhaW5seSBuZWVkcyB0aGUgYW1pbm8gYWNpZCB0cnlwdG9waGFuIHRvIHN5bnRoZXNpemUgcHJvdGVpbnMsIGJ1dCBubyBtb3JlIHRoYW4gYW55IG90aGVyIGFtaW5vIGFjaWQu[Qq]
[c]IGlzIHNvbWV0aW1lcyBhdmFpbGFibGUgaW4gdGhlIGVudmlyb25tZW50OyBtYWtpbmcg dHJ5cHRvcGhhbsKgY29udGludW91c2x5IHdvdWxkIGJlIGEgd2FzdGUgb2YgZW5lcmd5[Qq]
[f]IFllcy7CoEJlY2F1c2UgdHJ5cHRvcGhhbiBpcyBvY2Nhc2lvbmFsbHkgYXZhaWxhYmxlIGZyb20gdGhlIGVudmlyb25tZW50LMKgbWFraW5nIHRyeXB0b3BoYW7CoGNvbnRpbnVvdXNseSB3b3VsZCBiZSBhIHdhc3RlIG9mIGVuZXJneQ==[Qq]
[c]IGFjdHMgdG8gdHVybiBvbiB0aGUgdHJhbnNjcmlwdGlvbiBvZiB0aGUgc3RydWN0dXJhbCBnZW5lcyBmb3IgdHJ5cHRvcGhhbiBzeW50aGVzaXMu[Qq]
[f]IE5vLiBJbiB0aGUgdHJwIG9wZXJvbiBzeXN0ZW0sIHRyeXB0b3BoYW4mIzgyMTc7cyBwcmVzZW5jZSB0dXJucyBvZmYgdGhlIHRyYW5zY3JpcHRpb24gb2YgdGhlIHN0cnVjdHVyYWwgZ2VuZXMu[Qq]
[c]IGlzIGFuIGltcG9ydGFudCBlbmVyZ3kgc291cmNlIGZvciBFLiBjb2xp[Qq]
[f]IE5vLiBZb3UgbWlnaHQgYmUgdGhpbmtpbmcgYWJvdXQgdGhlIGxhYyBvcGVyb24sIHdoaWNoIGlzIGFib3V0IGRpZ2VzdGluZyB0aGUgc3VnYXIgbGFjdG9zZSwgYSBzb3VyY2Ugb2YgZW5lcmd5IGFuZCBtYXR0ZXIgZm9yIEUuIGNvbGkuIFRoZSB0cnAgb3Blcm9uIHN5c3RlbSBpcyBhYm91dCBFLiBjb2xpJiM4MjE3O3MgYWJpbGl0eSB0byBjb250cm9sIG1ldGFib2xpYyBwYXRod2F5cyBmb3Igc3ludGhlc2l6aW5nIG5lZWRlZCBzdWJzdGFuY2VzIChpbiB0aGlzIGNhc2UsIHRoZSBhbWlubyBhY2lkIHRyeXB0b3BoYW4pLg==
Cg==[Qq]
[q json=”true” dataset_id=”Operons|1d3c1fc5adff00″ question_number=”35″ multiple_choice=”true”] The structural genes in the trp operon system are only transcribed when
[c]IHRyeXB0b3BoYW4gaXMgcHJlc2VudCBhbmQgYmluZHMgd2l0aCB0aGUgcmVwcmVzc29yIHByb3RlaW4=[Qq]
[f]IE5vLiBJbiB0aGUgdHJwIG9wZXJvbiwgdGhlIHJlZ3VsYXRvcnkgc2NoZW1lIGlzIGFib3V0IGF2b2lkaW5nIHN5bnRoZXNpemluZyBhIG5lZWRlZCBzdWJzdGFuY2Ugd2hlbiB0aGF0IHN1YnN0YW5jZSBpcyBmcmVlbHkgYXZhaWxhYmxlIGZyb20gdGhlIGVudmlyb25tZW50LiBJbiBvdGhlciB3b3JkcywgdGhlIHN0cnVjdHVyYWwgZ2VuZXMgKHdoaWNoIGNvZGUgZm9yIGVuenltZXMgdGhhdCBzeW50aGVzaXplIHRyeXB0b3BoYW4pIGFyZSBvbmx5IHRyYW5zY3JpYmVkIHdoZW4gdHJ5cHRvcGhhbiBpcyBhYnNlbnQu[Qq]
[c]IFRoZSByZXByZXNzb3IgcHJvdGVpbiBpcyBhdHRhY2hlZCB0byB0aGUgb3BlcmF0b3IgZ2VuZQ==[Qq]
[f]IE5vLiBXaGVuIHRoZSByZXByZXNzb3IgcHJvdGVpbiBpcyBhdHRhY2hlZCB0byB0aGUgb3BlcmF0b3IgZ2VuZSwgdGhlIFJOQSBwb2x5bWVyYXNlIGlzIGJsb2NrZWQgYW5kIGNhbiYjODIxNzt0IHRyYW5zY3JpYmUgdGhlIHN0cnVjdHVyYWwgZ2VuZXMuIEluIHRoZSB0cnAgb3Blcm9uLCB0aGlzIG9ubHkgb2NjdXJzIGluIHRoZSBhYnNlbmNlIG9mIHRyeXB0b3BoYW4u[Qq]
[c]IHRyeXB0b3BoYW4gYmluZHMgdG8gUk5BIHBvbHltZXJhc2U=[Qq]
[f]IE5vLiBUaGUgdHJwIG9wZXJvbiBzeXN0ZW0gd29ya3MgdGhyb3VnaCB0aGUgcmVwcmVzc29yIHByb3RlaW4gYmluZGluZyB0byB0aGUgb3BlcmF0b3IgcmVnaW9uLCB3aGljaCBibG9ja3MgUk5BIHBvbHltZXJhc2UgZnJvbSB0cmFuc2NyaWJpbmcgdGhlIHN0cnVjdHVyYWwgZ2VuZXMuIE5vdGhpbmcgaW4gdGhpcyBzeXN0ZW0gYmluZHMgZGlyZWN0bHkgdG8gUk5BIHBvbHltZXJhc2Uu[Qq]
[c]IHRoZSBjby1yZXByZXNzb3IgKHRy eXB0b3BoYW4pIGlzIGFic2VudC4=[Qq]
[f]IEV4Y2VsbGVudC4gSW4gdGhlIHRycCBvcGVyb24gc3lzdGVtLCB0cnlwdG9waGFuIGFjdHMgYXMgYSBjby1yZXByZXNzb3IuIEl0JiM4MjE3O3Mgb25seSB3aGVuIHRyeXB0b3BoYW4gaXMgYWJzZW50IHRoYXQgdGhlIHN0cnVjdHVyYWwgZ2VuZXMgaW4gdGhpcyBvcGVyb24gKHdoaWNoIGNvZGUgZm9yIGVuenltZXMgdGhhdCBzeW50aGVzaXplIHRyeXB0b3BoYW4pIGFyZSB0cmFuc2NyaWJlZC4=[Qq]
[q]The diagram below represents what happens when E. coli is provided with both glucose and lactose. In the diagram below, the letter that represents glucose is
[textentry single_char=”true”]
[c]IF g=[Qq]
[f]IFllcy4g4oCcWOKAnSBpcyBnbHVjb3NlLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBXaGVuIGEgbWljcm9iZSBpcyBwcmVzZW50ZWQgd2l0aCB0d28gc3Vic3RhbmNlcyB0byBkaWdlc3QsIGl0IHdpbGwgZGlnZXN0IHRoZSBzaW1wbGVyIG9uZSBmaXJzdC4=[Qq]
[q] The diagram below represents what happens when E. coli is provided with both glucose and lactose. The letter that represents the moment when sufficient enzymes have been generated to digest lactose is
[textentry single_char=”true”]
[c]IE M=[Qq]
[f]IFllcy4gQXQgcG9pbnQg4oCcYywmIzgyMjE7IHRoZSA=bGFjIG9wZXJvbiBoYXMgYmVlbiBhY3RpdmF0ZWQsIGFuZCBlbnp5bWVzIGFyZSBhdmFpbGFibGUgZm9yIGRpZ2VzdGluZyBsYWN0b3NlLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBBZnRlciBhbGwgb2YgdGhlIGdsdWNvc2UgaGFzIGJlZW4gbWV0YWJvbGl6ZWQsIHRoZSBtaWNyb2JlIHdpbGwgc3RhcnQgZGlnZXN0aW5nIGxhY3Rvc2UuIExpbmUgWCB0ZWxscyB5b3Ugd2hlbiBhbGwgb2YgdGhlIGdsdWNvc2UgaGFzIGJlZW4gY29uc3VtZWQuIEF0IHdoYXQgcG9pbnQgb24gdGhlIHJlZCBsaW5lIGRvZXMgZ3Jvd3RoIHJlc3VtZT8=[Qq]
[q] The diagram below represents what happens when E. coli is provided with both glucose and lactose. The letter that represents the moment when growth pauses as the lac operon gets activated is represented by
[textentry single_char=”true”]
[c]IG I=[Qq]
[f]IFllcy4gRHVyaW5nICYjODIyMDtiJiM4MjIxOyB0aGUgbGFjIG9wZXJvbiBpcyBiZWluZyBhY3RpdmF0ZWQsIGNyZWF0aW5nIGVuenltZXMgdGhhdCB3aWxsIGVuYWJsZSA=RS4gY29saQ==IHRvIHN0YXJ0IGRpZ2VzdGluZyBsYWN0b3NlLg==[Qq]
[c]ICo=[Qq]
[f]IE5vLiBIZXJlJiM4MjE3O3MgYSBoaW50LiBBZnRlciBhbGwgb2YgdGhlIGdsdWNvc2UgaGFzIGJlZW4gbWV0YWJvbGl6ZWQsIHRoZSBtaWNyb2JlIHByb2R1Y2VzIGxhY3Rvc2UtZGlnZXN0aW5nIGVuenltZXMuIEFzIGl0IGRvZXMgdGhpcywgdGhlcmUgd2lsbCBiZSBhIHBhdXNlIGluIGdyb3d0aCB1bnRpbCBzdWZmaWNpZW50IGFtb3VudHMgb2YgbGFjdG9zZS1kaWdlc3RpbmcgZW56eW1lcyBoYXZlIGJlZW4gZ2VuZXJhdGVkLiBXaGljaCBsZXR0ZXIgY291bGQgaW5kaWNhdGUgYSBwYXVzZSBpbiBncm93dGg/[Qq]
[/qwiz]
What’s Next?
Please proceed to our next tutorial: Eukaryotic Gene Regulation