Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 16, Problem 13PDQ
Summary Introduction
To explain: The widespread occurrence of attenuation as a way of genetic regulation, although it is a relatively inefficient way.
Introduction: Transcription of genes is regulated by different feedback pathways. These regulatory pathways involve repressor or inducer molecules. Increase or decrease in the concentration of the target molecule in the body activates more positive or negative feedback control.
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Students have asked these similar questions
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)
Attenuation of the trp operon was viewed as a relatively inefficient way to achieve genetic regulation when it was first discovered in the 1970s. Since then, however, attenuation has been found to be a relatively common regulatory strategy. Assuming that attenuation is a relatively inefficient way to achieve genetic regulation, what might explain its widespread occurrence?
Suppose you are studying the regulation of a gene involved in the metabolism of two nutrients, Llamasin and Alpacalon, in bacteria. You are trying to determine if these nutrients act as inducers in their operons. The following data were collected from your experiments. Which of these operons is most similar to the lac operon? Explain.
Nutrient
Levels of nutrient in growth medium
Level of transcription of genes in operon
Llamasin
low
high
high
low
Alpacalon
low
low
high
high
Highlight one in green:
Llamasin Alpacalon
Explanation:
Chapter 16 Solutions
Concepts of Genetics (12th Edition)
Ch. 16 - Even though the lac Z, Y, and A structural genes...Ch. 16 - Predict the level of genetic activity of the lac...Ch. 16 - Prob. 1CSCh. 16 - Prob. 2CSCh. 16 - Prob. 3CSCh. 16 - HOW DO WE KNOW? In this chapter, we focused on the...Ch. 16 - Prob. 2PDQCh. 16 - Contrast positive versus negative control of gene...Ch. 16 - Contrast the role of the repressor in an inducible...Ch. 16 - For the lac genotypes shown in the following...
Ch. 16 - For the genotypes and conditions (lactose present...Ch. 16 - The locations of numerous lacI and lacIS mutations...Ch. 16 - Prob. 8PDQCh. 16 - Prob. 9PDQCh. 16 - Predict the effect on the inducibility of the lac...Ch. 16 - Erythritol, a natural sugar abundant in fruits and...Ch. 16 - Prob. 12PDQCh. 16 - Prob. 13PDQCh. 16 - Neelaredoxin is a 15-kDa protein that is a gene...Ch. 16 - The creation of milk products such as cheeses and...Ch. 16 - Both attenuation of the trp operon in E. coli and...Ch. 16 - Prob. 17PDQCh. 16 - Prob. 18ESPCh. 16 - In a theoretical operon, genes A, B, C, and D...Ch. 16 - A bacterial operon is responsible for the...Ch. 16 - A marine bacterium is isolated and shown to...Ch. 16 - Prob. 22ESPCh. 16 - Prob. 23ESP
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- Let’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_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_forwardYou can determine the regulation of an unknown operon based on descriptions like those in the table below. For each row, choose whether the fact would suggest positive or negative or inducible or repressible regulation and indicate your answer with an X in the column. Only one X should appear in each row. In the presence of the signal, the structural genes are expressed. In the presence of the signal, the structural genes are not expressed. In the absence of the signal, the structural genes are expressed. In the absence of the signal, the structural genes are not expressed. The binding of the regulatory protein to the operon results in structural gene expression. The binding of the regulatory protein to the operon prevents structural gene expression. A mutation in the regulatory protein results in constitutive expression of the structural genes. A mutation in the regulatory protein results in no or low expression of the structural genes. Positive? Negative? Inducible? Repressible?arrow_forward
- A theoretical operon (theo) in E. coli contains several structural genes encoding enzymes that are involved sequentially in the biosynthesis of an amino acid. Unlike the lac operon, in which the repressor gene is separate from the operon, the gene encoding the regulator molecule is contained within the theo operon. When the end product (the amino acid) is present, it combines with the regulator molecule, and this complex binds to the operator, repressing the operon. In the absence of the amino acid, the regulatory molecule fails to bind to the operator, and transcription proceeds. Characterize this operon, then consider the following mutations, as well as the situation in which the wild-type gene is present along with the mutantgene in partially diploid cells (F¿):(a) Mutation in the operator region.(b) Mutation in the promoter region.(c) Mutation in the regulator gene.In each case, will the operon be active or inactive in transcription, assuming that the mutation affects the…arrow_forwardFor the following questions, describe the expression levels of the structural genes in the Trp operon under the conditions described. In the absence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the trpR repressor gene is mutated such that the…arrow_forwardFor the following questions, describe the expression levels of the structural genes in the Trp operon under the conditions described. In the absence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"]arrow_forward
- Examine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Question 1 Promoter Operator genC genB gen operon Regulator genA Transcription occurs when: A. The amino acid is not bound to the regulator, causing the regulator to bind to the operator. B. The amino acid is bound to the regulator, causing the regulator to bind to the operator. C. The amino acid is not bound to the regulator, causing the regulator to fail to bind to the operator. D. The amino acid is bound to the regulator, causing the regulator to fail to bind to the operator. E. The operon is…arrow_forwardExamine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genAarrow_forwardWhich 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_forward
- You have isolated different mutants (reg1 and reg2) causing constitutive expression of the emu operon (which has genes emu1 and emu2). One mutant contains a defect in a DNA-binding site, and the other has a loss-of-function defect in the gene encoding a protein that binds to the site Say you don’t know which mutant has a defect in the site and which one has a mutation in the binding protein. To figure it out, you construct the two partial diploid strains (i and ii below), and you then assay the levels of the Emu1 and Emu2 proteins in these two strains. F’ (reg1- reg2+ emu1- emu2+) / reg1+ reg2+ emu1+ emu2- F’ (reg1+ reg2- emu1- emu2+) / reg1+ reg2+ emu1+ emu2- What proteins do you predict will be expressed for strains i and ii if reg2 encodes the regulatory protein and reg1 is the regulatory site?arrow_forwardLike the lac operon, the hexose operon is controlled by a separate regulatory protein under the control of its own promoter (see the schematic of the operon below). The hexose regulatory protein is sensitive to fatty acyl CoA levels. When all hexose fuel sources are depleted, the bacteria switch to lipid metabolism and fatty acyl CoA levels increase. This turns expression of the hexose operon off. +1 +1 Regulatory Gene regulator Hexose Operon Genes operon regulator promoter operon promoterarrow_forwardRemember that hexose kinase is an enzyme required for hexose metabolism, a process that takes a 6-carbon sugar and breaks it down into 2 pyruvate molecules. You discover that rather than being hormonally regulated (as seen above in humans), hexose kinase is part of an operon in prokaryotic organisms. This operon is known as the "hexose operon" and it regulates expression of the complete set of enzymes needed to convert a hexose sugar into 2 pyruvate molecules. Like the lac operon, the hexose operon is controlled by a separate regulatory protein under the control of its own promoter (see the schematic of the operon below). The hexose regulatory protein is sensitive to fatty acyl CoA levels. When all hexose fuel sources are depleted, the bacteria switch to lipid metabolism and fatty acyl COA levels increase. This turns expression of the hexose operon off. +1 +1 Regulatory Gene Pregulator Por operon Hexose Operon Genes regulator promoter operon promoter Question 5 E) The regulatory…arrow_forward
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