Genetics: Analysis and Principles
6th Edition
ISBN: 9781259616020
Author: Robert J. Brooker Professor Dr.
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 14, Problem 11CONQ
Mutations may have an effect on the expression of the lac operon and the trp operon. Would the following mutations have acis- or trans-effect on the expression of the protein-encoding genes in the operon?
A. A mutation in the operator site that prevents lac repressor from binding to it
B. A mutation in the lacI gene that prevents lac repressor from binding to DNA
C. A mutation in the trpL gene that prevents attenuation.
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Mutations may have an effect on the expression of the lac operon and the trp operon. Would the following mutations have a cis- or transeffect on the expression of the protein-encoding genes in the operon?
A. A mutation in the operator site that prevents lac repressor from binding to it
B. A mutation in the lacI gene that prevents lac repressor from binding to DNA
C. A mutation in the trpL gene that prevents attenuation
A mutation in the operator region of the trp operon can prevent the trp repressor from binding to this operator. When these mutant cells are placed in a solution containing chicken broth, which of the following happens?
a. Tryptophan would bind to the repressor.
b. The Repressor would bind to the operator irrespective of the presence of amino acids in the environment.
c. The transcription of the trip operon would be inhibited.
d. The transcription of the repressor protein is inhibited
Mutations in the genes of the lac operon might affect the regulation of β-galactosidase synthesis. For each mutation listed below, indicating whether β-galactosidase would be regulated normally, always ON or always OFF.
a. Mutation in operator site prevents repressor binding
b. Mutation in lacIgene prevents repressor from binding operator
c. Mutation in lacIgene prevents repressor from binding allolactose
d. Nonsense mutation in lacZgenere
Chapter 14 Solutions
Genetics: Analysis and Principles
Ch. 14.1 - 1. A repressor is a __________ that _________...Ch. 14.1 - 2. Which of the following combinations will cause...Ch. 14.2 - 1. What is an operon?
a. A site in the DNA where...Ch. 14.2 - The binding of _______ to lac repressor causes lac...Ch. 14.2 - Prob. 3COMQCh. 14.2 - How does exposing an E. coli cell to glucose...Ch. 14.3 - When tryptophan binds to trp repressor, this...Ch. 14.3 - During attenuation, when tryptophan levels are...Ch. 14.3 - Operons involved with the biosynthesis of...Ch. 14.4 - 1. Translation can be regulated by
a....
Ch. 14.4 - Prob. 2COMQCh. 14.5 - 1. For a riboswitch that controls transcription,...Ch. 14 - 1. What is the difference between a constitutive...Ch. 14 - In general, why is it important to regulate genes?...Ch. 14 - Prob. 3CONQCh. 14 - Transcriptional regulation often involves a...Ch. 14 - An operon is repressible-a small effector molecule...Ch. 14 - Prob. 6CONQCh. 14 - 7. What is enzyme adaptation? From a genetic point...Ch. 14 - Prob. 8CONQCh. 14 - Prob. 9CONQCh. 14 - Prob. 10CONQCh. 14 - Mutations may have an effect on the expression of...Ch. 14 - 12. Would a mutation that inactivated lac...Ch. 14 - Prob. 13CONQCh. 14 - 14. As shown in Figure 14.12, four regions within...Ch. 14 - 15. As described in Chapter 13, enzymes known as...Ch. 14 - 16. The combination of a 3–4 stem-loop and a...Ch. 14 - 17. Mutations in tRNA genes can create tRNAs that...Ch. 14 - Prob. 18CONQCh. 14 - Prob. 19CONQCh. 14 - A species of bacteria can synthesize the amino...Ch. 14 - 21. Using three examples, describe how allosteric...Ch. 14 - How are the actions of lac repressor and trp...Ch. 14 - 23. Transcriptional repressor proteins (e.g., lac...Ch. 14 - Answer the following questions that pertain to the...Ch. 14 - Chapter 21 describes a blotting method known as...Ch. 14 - As described in experimental question E2 and also...Ch. 14 - Prob. 4EQCh. 14 - Explain how the data shown in Figure 14.9 indicate...Ch. 14 - Prob. 6EQCh. 14 - Lets suppose you have isolated a mutant strain of...Ch. 14 - Prob. 1QSDCCh. 14 - Prob. 2QSDC
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- Study the depiction of the lac operon in Figure 11.2. Normally, the genes are turned off when lactose is not present. Lactose activates the genes, which code for enzymes that enable the cell to use lactose. Mutations can alter the function of this operon. Predict how the following mutations would affect the function of the operon in the presence and absence of lactose: a. mutation of regulatory gene; repressor will not bind to lactose b. mutation of operator; repressor will not bind to operator c. mutation of regulatory gene; repressor will not bind to operator d. mutation of promoter; RNA polymerase will not attach to promoterarrow_forwardDefine the following in the context of operons: a. positive control b. give an example of an operon that is under positive control c. negative control d. give an example of an operon that is under negative control e. repressor f. give an example of a repressor molecule g. activator h. give an example of an activatorarrow_forwardControl of the trp operon relies on which of the following: a. High levels of tryptophan causing a pause (but not termination) in transcription b. Low levels of tryptophan causing a pause (but not termination) in transcription c. Allolactose binding to the inhibitor to prevent it from binding to the promoter d. Tryptophan binding to the inhibitor to prevent it from binding to the promoterarrow_forward
- 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 a.Which operons would be functional under these conditions? b.What repressors would be made? (NOTE: name the repressors using their gene names) c.Which repressor(s) would be made in the inactive form? d.Which repressor(s) would be made in the active form? e.Which repressor(s) under these conditions can bind the operator sequence? f.Which repressor(s)under these conditions cannot bind the operator sequence?arrow_forwardIndicate whether each of the following statements about the lac operon are true or false: Bacteria with a lac phenotype are unable to use lactose because of some defect in expressing the genes A constitutive Lac+ phenotype could mean either that the production of repressor is defective or that the operator sequence is defective The lacl gene is next to, but is not part of, the lac 1. TRUE operon 2. FALSE Bacteria with a lac* phenotype cannot grow on media containing lactose as the only sugar The structural genes of the lac operon are each transcribed as a separate MRNA Expression of the Lac Repressor from the lacl promoter is regulated by lactosearrow_forwardIf CAP is bound to the Promoter of the Lac Operon and the repressor protein is not bound to the operator, which of the following is true: a.Glucose Levels are low & Lactose is absent b.Glucose is absent & Lactose is present c.cAMP is low & Lactose is Absent d.Glucose and Lactose are Present e.cAMP is low & Lactose is presentarrow_forward
- When iron is scarce, some bacteria can stop synthesis of all enzymes that require iron (Fe3+), such as superoxide dismutase (SOD). Which of the following accurately describes a mechanism for this regulation? Mark all that apply. A. Regulation occurs by an inducible operon B. When absent, the lack of iron causes the repressor to deactivate and block the promoter region for these genes C. Regulation occurs by a repressible operon D. When present, iron binds and activates the repressor proteinarrow_forwardOne way that regulation is often studied is by examining the effects of mutations. For example, mutations within the parts of the lac operon have been well studied. Which of these mutants would be considered a constitutive mutant (the operon is always on)? a mutation in CAP that prevents the binding of CAMP a mutation in one of the structural genes that prevents the transport of lactose into the cell a mutation that disables the promoter for the operon a mutation that disables the repressorarrow_forwardWhat would happen if the operator sequence of the lac operon contained a mutation that prevented the repressor protein from binding the operator? (Explain what would happen both in the presence and absence of lactose)arrow_forward
- A mutation at the operator prevents the regulator protein from binding. What effect will this mutation have in the following types of operons? a. Regulator protein is a repressor of a repressible operon. b. Regulator protein is a repressor of an inducible operon.arrow_forwardAll of the following statements about the repressor of the lac operon of E. coli are true EXCEPT which one? O A. The repressor is the product of a regulatory gene i The repressor binds to the operator region of the DNA of the lac OB. operon. The repressor is a protein. OC. The repressor interacts with the operator in such a way as to OD. prevent translation of beta-galactosidase. The repressor can combine with lactose to form a OE. complex that will no longer bind to the operator region. QUESTION 32 The amino acid which is a precursor of serotonin is Histidine OA. O B. Tyrosine O C. Glutamate D. Tryptophan O E. none of the abovearrow_forwardThe lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) I+ OC Z+ I+ O+ Z+ (Lactose present) I- O+ Z+arrow_forward
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