DNA RNA polymerase mRNA Polypeptide Folding Repressor protein Medium Operon P Z Y A Structural genes Lactose mRNA mRNA OOOOOO 0000000 0000 B-Galactosidase Permease Transacetylase A. In prokaryotic cells, how does the lac operon work in a low lactose concentration? B. In prokaryotic cells, how does the lac operon work in a high lactose concentration? ? [Note: To receive full credit, you must include in your answer at least the roles of Lacl, inducer, promoter, operator, and structural genes]

DNA RNA polymerase mRNA Polypeptide Folding Repressor protein Medium Operon P Z Y A Structural genes Lactose mRNA mRNA OOOOOO 0000000 0000 B-Galactosidase Permease Transacetylase A. In prokaryotic cells, how does the lac operon work in a low lactose concentration? B. In prokaryotic cells, how does the lac operon work in a high lactose concentration? ? [Note: To receive full credit, you must include in your answer at least the roles of Lacl, inducer, promoter, operator, and structural genes]

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter16: Gene Expression

Section: Chapter Questions

Problem 9RQ: The a/a operon is an inducible operon that controls the production of the sugar arabinose. When...

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amount of protein / amount of mRNA 12 mm / ↑ A B time (minutes) 20 Bacteria were grown in culture. At various time points, substances were added or removed from the culture medium. To assay the effects of the substances on operon gene expression, samples of bacteria were collected at one-minute intervals and levels of specific proteins and mRNAs were determined. If the operon under investigation is a repressible operon, which arrow indicates the addition of a molecule that binds the repressor protein?
Answer as Directed. Below is the model of a lac operon. lac I lac Z с promoter operator +1 lac Y lac A DNA 1. In the absence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac control region? Is the operon being transcribed then? 2. In the presence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac regulatory region? Is the operon being transcribed then? 3. In the presence of lactose and the absence of glucose in the bacterial growth media, what proteins are bound to the lac control region? 4. Why is it adaptive for a bacterium to not express the genes that encode for that lactose utilization proteins when lactose is not available or when glucose is present? 5. Why is it adaptive for the structural genes for using lactose to be under the control of a single promoter, i.e., synthesize a polycistronic message rather than three monocistronic message?
Read aloud V Draw Highlight 2. You are studying the regulation of the lactose operon in Escherichia coli, by measuring expression of the lacZ gene (i.e production of beta-galactosidase). (a) You identify several loss-of-function mutations in which lacZ is never expressed, in the presence and absence of glucose and lactose. What components of the lac operon could be mutated to produce this phenotype? List all possibilities. (b) You identify another loss-of-function mutation with the following expression pattern: Media + glucose - lactose + glucose +lactose - glucose - lactose - glucose + lactose lacZ expression Low Low High High What components of the lac operon could be mutated to produce this phenotype? List all possibilities.
Answer as Directed. Below is the model of a lac operon. lac I lac Z с promoter operator lac Y lac A DNA +1 1. What are structural genes? Are the lac structural genes transcribed in the absence of lactose? 2. What is the role of the promoter and operator sites in the operon? 3. Is the repressor protein bound to the operator site in the absence of lactose? In its absence? 4. Under what nutritional circumstances (high or low glucose) is CAP bound to cAMP? 5. In the absence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac control region? Is the operon being transcribed then? 6. In the presence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac regulatory region? Is the operon being transcribed then? 7. In the presence of lactose and the absence of glucose in the bacterial growth media, what proteins are bound to the lac control region? 8. Why is it adaptive for a bacterium to not…
segment of DNA segment of DNA reproesor profein RHA polymerase RNA polymerase rupraesor profin Dlagram A Dlagram B Which diagram shows a system in which the lac operon genes are NOT going transcribed by the E. Coli?
Explain why (a) inactivation of the O2 or O3 sequence of the lac operon causes only a twofold loss in repression, and (b) inactivation of both O2 and O3 reduces repression ∼70-fold.
that best fits the phrase below (1-20) Cis-acting B Post-transcriptional modification Post-translational modification Reactive (R) group Trans-acting C Operon Nuclear localizationsignal Double-stranded RIA Shine-Dalgarno sequence Kozak sequence E site on ribosome Ps p riboeE8R3) A site on ribosome Constitutive F Allosteric transition Inducer ll ol g Repressor T G H. Nonsense codon Frameshift mutation W Chaperones Found upstream of AUG codons in bacteria, this binds the 3' end of the 16S rRNA of the 30S ribosomal subunit Addition of chemical groups to amino acids in a polypeptide Hidigel elnw eesel Poly (A) polymerase enzyme uses ATP as substrate to add a string of A nucleotides on to the 3'-OH of MRNA Jeiheg 1ot eninoaso uoy nielgxe 10 anoitamusas Tuoy elsta otehgo1qqs eedW 4 Is produced when both strands of DNA encoding a gene are transcribed simultaneously A class of proteins that arrest incorrectly or incompletely folded proteins 6. Occurs when allolactose binds Lacl protein causing…
Substrate Binding by RNA Polymerase RNA polymerase has t binding sites for ribonucleoside triphosphates: the initiation site and the elongation site. The initiation site has a greater Km for NTPs than the elongation site. Suggest what possible significance this fact might have for the control of transcription in cells.
The a/a operon is an inducible operon that controls the production of the sugar arabinose. When arabinose is present in a bacterium it binds to the protein AraC, and the complex binds to the initiator site to promote transcription. In this scenario, AraC is a(n). activator inducer repressor operator
Trp operon of E. coli is an inducible sytem since it turns on in the presence of tryptophan. In most bacteria, protein synthesis is initiated with a modified methionine residue (N-formylmethionine), whereas unmodified methionines initiate protein synthesis in eukaryotes. Both DNA replication and transcription follow a 5’ to 3’ direction of polarity. Write T if the statement is true and write F if the statement is false
Suppose that you have isolated a mutant strain of E. coli inwhich the lac operon is constitutively expressed. To understandthe nature of this defect, you create a merozygote in which themutant strain contains an F′ factor with a normal lac operonand a normal lacI gene. You then compare the mutant strain andthe merozygote with regard to their β-galactosidase activities inthe presence and absence of lactose. You obtain the followingresults:
The symbols a, b, and c in the table below represent theE. coli lac system genes for the repressor (I ), the operator(O) region, and the β-galactosidase (Z), although notnecessarily in that order. Furthermore, the order inwhich the symbols are written in the genotypes is notnecessarily the actual sequence in the lac operon.Activity (+) or inactivity (−) of Z geneGenotype Inducer absent Inducer presenta- b+ c+ + +a+ b+ c- + +a+ b- c- - a+ b- c+/a- b+ c- + +a+ b+ c+/a- b- c- - +a+ b+ c-/a- b- c+ - +a- b+ c+/a+ b- c- + +a. Which symbol (a, b, or c) represents each of the lacgenes I, O, and Z ?b. In the table, a superscript minus sign on a gene symbolmerely indicates a mutant, but some mutant behaviorsin this system are given special mutant designations.Using the conventional gene symbols for the lac operon,designate each genotype in the table.