1. In E.coli transcription of the Lac Operon is known to be under Global control. For this operon explain the mechanisms of both negative and positive control (be sure to identify relevant regulatory molecules and operon regions). A. Positive Transcriptional Control: B. Negative Transcriptional Control: C. If E.coli is grown in media containing both glucose and lactose when would you expect to see beta-galactosidase (catalyzes the hydrolysis of lactose) produced?

1. In E.coli transcription of the Lac Operon is known to be under Global control. For this operon explain the mechanisms of both negative and positive control (be sure to identify relevant regulatory molecules and operon regions). A. Positive Transcriptional Control: B. Negative Transcriptional Control: C. If E.coli is grown in media containing both glucose and lactose when would you expect to see beta-galactosidase (catalyzes the hydrolysis of lactose) produced?

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter16: Regulation Of Gene Expression

Section: Chapter Questions

Problem 11TYK: Discuss Concepts In a mutant strain of E. coli, the CAP protein is unable to combine with its target...

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For the E. coli lac operon, when lactose is present: a. and glucose is absent, cAMP binds and activates catabolicactivator protein (CAP). b. and glucose is absent, the level of cAMP decreases. c. activated CAP binds the repressor protein to remove it from the operator gene. d. the cell prefers lactose over glucose. e. RNA polymerase cannot bind to the promoter.
1. A)Explain the mechanism by which the lac operon is sensitive to glucose levels (presence and absence of glucose). B)If glucose levels in the cell are high and lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?
1. If the above gene is one of the three structural genes of the lac operon that codes for theprotein/ enzyme responsible for breaking lactose into two molecules of simple sugars,a.) what triggers the activation of this gene?b.) what triggers the inactivation of this gene?c.) what substance is attached to the operator region of the operon in the absence ofactivator?d.) what gene is responsible for the synthesis of the substance used to attach in theoperator region in the absence of activator? e.) what substance is attached to the promoter region of the operon in this case?
1. Assuming that the level of glucose is low, a mutation in the repressor associated with the lac operon of E. coli which prevents binding of the repressor to lactose should result in: a. constitutive expression of the lac operon genes b. lack of expression or refuced expression of the lac operon genes under all circumstances c. expression of the genes only when lactose is present d. expression of the genes only when lactose is absent e. lack of expression of the lac operon genes, resulting in an increase in lactose production
1) The logic of the Lac operon was deciphered by using bacterial lac-operon mutants. Crucial to the experiments was creation of partial diploid cells in which operon from a wild-type cell is introduced into the mutant cell [thus there are 2 copies of the operon], and its ability to restore repression is assessed. Three classes of mutants were found that affect expression of the lac operon. Two of these resulted in constitutive expression of the operon, and the other eliminated all expression, even in the presence of lactose. Use the information above to complete the following table indicating with a (Y) yes or (N= No) if enzymatic activity of B-Gal will be detected (protein made and functional). Assume there is no glucose. Remember: Promoter for operon controls ALL genes downstream of it, coding sequence of the genes themselves matter (so if transcription is occurring but structural gene is producing a non-functional protein there will be no activity detected) For the lac operon…
1) A. What is the difference between a repressible vs, an inducible operon? B. Using diagrams and words, describe how the Lac Operon is regulated by different levels of lactose and glucose. Be sure to show what’s happening at the molecular level, including the roles of lactose, glucose the repressor protein, cAMP and CAP.
1. a) If glucose is not available and lactose is absent from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon? b)If glucose is not available, but lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon? b)
1. What is the default state of the lac operon? a. LacI repressor is sitting on the operator sequence and blocks RNAP from transcribing lacZYA. b. LacI repressor is not in a correct shape to bind to the operator sequence. c. LacI repressor is not produced in the absence of lactose. d. Allolactose is sitting on the operator sequence and blocks RNAP from transcribing lacZYA.
There is Hyaluronic acid synthesis occuring in Group X Strep and it is controlled by an operon with 3 genes, called hasXYZ. Based on the 3-line diagram model, a. How many ribosome binding sites are there for the protein? b. How many promoters are there for the genes? c. How many start codons are there for the protein? d. How many RNA Polymerase binding locations are there for the genes? e. How many proteins will be fully functional? f. How many mRNA strands are made?
. In an effort to determine the location of an operator sitefor a negatively regulated gene, you have made a seriesof deletions within the regulatory region. The extent ofeach deletion is shown by the line underneath the sequence, and the resulting expression from the operon(i = inducible; c = constitutive; − = no expression) isalso indicated.... GGAT C T T AGCCGGCTAACATGATAAATATAA......C C T AGAATCGGCCGA TTGTA C T A TTT ATAT T ...1 i2 –3 c4 –5 ca. What can you conclude from these data about thelocation of the operator site?b. Why do you think deletions 2 and 4 show no expression of the gene?
One of the main lessons of this chapter is that severalbacterial genes are often transcribed from a singlepromoter into a large multigene (polycistronic) transcript. The region of DNA containing the set of genesthat are cotranscribed, along with all of the regulatoryelements that control the expression of these genes, iscalled an operon.a. Which of the mechanisms in the following listcould explain differences in the levels of themRNAs for different operons?b. Which of the mechanisms in the following listcould explain differences in the levels of theprotein products of different genes in the sameoperon?i. Different promoters might have different DNAsequences.ii. Different promoters might be recognized bydifferent types of RNA polymerase.iii. The secondary structures of mRNAs might differ so as to influence the rate at which they aredegraded by ribonucleases.PROBLEMSProblems 575a. Why did the mating with a nonlysogenic recipientresult in phage growth and release, but the infectionof a…
1. The following are genotypes of merozygotes of E. coli with various combinations of lac operon mutations. Determine the phenotype with respect to beta-galactosidase (z), permease (y), and trans-acetylase (a) of each combination as U = uninducible, I = inducible, and C = constitutive. Choose from the following answers. i- p+ o+ z+ y- a+ / i+ p+ oc z- y- a+ Answer choices UII UIC UUU ICC CUC IUC CCU 2. The following are genotypes of merozygotes of E. coli with various combinations of lac operon mutations. Determine the phenotype with respect to beta-galactosidase (z), permease (y), and trans-acetylase (a) of each combination as U = uninducible, I = inducible, and C = constitutive. Choose from the following answers. i- p+ o+ z- y+ a+ / iS p+ o+ z- y+ a+ Answer choices ICC CCU UII IUC UIC CUC UUU