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 12CONQ
Would a mutation that inactivated lac repressor and prevented it from binding to the lac operator site result in the constitutive expression of the lac operon under all conditions? Explain. What is the disadvantage to the bacterium of having a constitutive lac operon?
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What 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)
What would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)
Suppose that E. coli sustains a mutation in its gene for the lac operon repressor such that the repressor is ineffective. What effect would this have on the bacterium’s ability to catabolize lactose? Would the mutant strain have an advantage over wild-type cells? Explain your answer.
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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- Explain why inactivation of the O1 sequence of the lac operator almost completely abolishes repression of the lac operon.arrow_forwardIf 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?arrow_forwardIn the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answerarrow_forward
- Which of the following lac operon genotypes would allow for functional versions of all the structural enzymes of the lac operon to be expressed constitutively even in the absence of lactose? Group of answer choices I+ O+ Z+ Y+ A+ I- O+ Z- Y- A- I+ OC Z+ Y+ A+ IS O+ Z+ Y+ A+ I+ O+ Z- Y+ A+arrow_forwardSuppose that E. coli sustains a mutation in its gene for the lac operon depressor making the repressive ineffective. How would this mutation affect the bacterium's ability to catabolize lactose? Would the mute to strain have an advantage over the wild-type strain?arrow_forwardStrain P77 has a mutation in the lacO that prevents it from being bound by the lacI protein. Otherwise all other parts of the operon are functional. 1. Can strain P77 metabolize lactose if it is present? 2. If lactose is absent, will strain P77 transcribe its lac operon? 3. If lactose is present, will strain P77 transcribe its lac operon?arrow_forward
- Strain ROFL4 has a premature stop mutation in the lacZ gene, resulting in a nonfunctional b-galactosidase. Otherwise all other parts of the operon are functional. 1. Can strain ROFL4 metabolize lactose if it is present? 2. If lactose is absent, will strain ROFL4 transcribe its lac operon? 3. If lactose is present, will strain ROFL4 transcribe its lac operon?arrow_forwardStrain HK180 has lac operon with a nonfunctional lacP. Otherwise all other parts of the operon are functional. 1. Can strain HK180 metabolize lactose if it is present? 2. If lactose is absent, will strain HK180 transcribe its lac operon? 3. If lactose is present, will strain HK180 transcribe its lac operon?arrow_forwardLet’s suppose you have isolated a mutant strain of E. coli in which the lac operon is constitutively expressed. In other words, the operon is turned on in the presence or absence of lactose. One possibility is that the mutation mayblock the transcription of the lacI gene, thereby preventing the synthesis of lac repressor. A second possibility is that the mutation could alter the sequence of the lac operator in a way that prevents lac repressor from binding to the operator. How would you distinguish between these two possibilities?arrow_forward
- Imagine that a new strain of E. coli is discovered, and it contains the following novel genetic region including the lacI gene and the lac operon: *see image* Upstream of the promoter associated with the lac operon, there is a new operator element "Oν" (O-"nu"). This new operator has high sequence homology to O1, the DNA element that is bound with the highest affinity by the lac repressor. What would be the impact of this new genetic element regarding behavior of the operonin the absence (vs. the presence) of lactose and allolactose? Answer in terms of the protein levels of the lac repressor, as well as the proteins encoded by the genes lacZ/Y/A in the downstream region of the operon. Remember that proteins, once expressed/generated, will not persist forever, and that they have a natural lifetime (ending when they are degraded by the cell).arrow_forwardSuppose that E. coli sustains a mutation in its gene for the lac operon repressor making the repressor ineffective . How would this mutation affect the bacterium's ability to catabolize lactose? Would the mutant strain have an advantage over the wild-type strain? Explain your answer.arrow_forwardSuppose that E. coli sustains a mutation in its gene for the lac operon repressor making the repressor ineffective. How would this mutation affect the bacterium's ability to catabolize lactose?arrow_forward
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