1. The lactose operon is controlled by both lactose and glucose. Fill in the following table to indicate what would be occurring under different cellular conditions Lactose absent present absent present Glucose Operon Activity (high/low) absent absent present present lov high 10W high Repressor CAMP (bound/free) (high/low) bound free bound will high high low low CAP (bound/free) bound bound

1. The lactose operon is controlled by both lactose and glucose. Fill in the following table to indicate what would be occurring under different cellular conditions Lactose absent present absent present Glucose Operon Activity (high/low) absent absent present present lov high 10W high Repressor CAMP (bound/free) (high/low) bound free bound will high high low low CAP (bound/free) bound bound

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 2TYK: For the E. coli lac operon, when lactose is present: a. and glucose is absent, cAMP binds and...

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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. 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. 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. 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) Assume you have an operon that is repressible. In this case, the rate of synthesis of repressor protein must depend on the level of a) co-repressor b) inducer c) both d) neither
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. 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
You are growing E. coli in a laboratory in order to study their operons. The growth media you are using contains lactose, no glucose and no tryptophan. Using your knowledge of operons and their regulation, answer the following questions Which operons would be functional under these conditions? 2. What repressors would be made? (NOTE: name the repressors using their gene names) 3.Which repressor(s) would be made in the inactive form? 4.Which repressor(s) would be made in the active form? 5.Which repressor(s) under these conditions can bind the operator sequence? 6.Which repressor(s)under these conditions cannot bind the operator sequence?
1. In DNA amplification, using the Taq polymerase, what is the maximum number of amplification cycles? a. 30 b. 20 c. 60 d. 10 2. In the case of trp operon, for transcription to fully occur, which of the following conditions must be met? a. Environmental tryptophan level must be low. b. Environmental tryptophan must be absent. c. Environmental tryptophan level must be abundant. d. Both a and b are correct.
. 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?
A haploid E. coli cell has the genotype I ¯ P+ O+ Z+ Y ¯ where the I ¯ indicates that the repressor protein cannot bind to the operator due to a mutation. Which of the following statements about cells with this lac operon genotype are correct? I ¯ P+ O+ Z+ Y ¯ Select all that apply. β-galactosidase will be transcribed constitutively. The cells are able to import lactose across the cell membrane. The cells are lac+ and are able to grow on a medium with lactose but no glucose. RNA polymerase can bind to the promoter.