Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 16, Problem 5P
The figure at the beginning of this chapter shows the binding of both a Lac repressor tetramer and a CRP-cAMP
complex to the regulatory region of the lac operon.
a. | What is the key feature of a regulatory protein such as the Lac repressor or CRP that allows it to regulate specifically the genes or operons it is supposed to control? |
b. | On the figure, show the positions of the following components: (i) A Lac repressor monomer; (ii) a Lac repressor dimer; (iii) all four DNA binding domains of the Lac repressor tetramer; (iv) a single helix-turn helix motif; (v) the o part and either the o or o parts of the lac operator (assume the operon would be transcribed from right to left on the figure); (vi) the multimerization domains of the four Lac repressor monomers; (vii) an inducer-interacting domain; (viii) the CRP-cAMP complex; and (ix) a DNA loop. |
c. | What is the physical basis for the formation of the DNA loop shown in the figure? |
d. | On the figure, show the position of two axes of symmetry in the sequence of DNA. How do you know, only on the basis of the figure and without prior information about the precise DNA sequence, that these two axes of symmetry are likely to be present in the DNA and that the sequences around these axes are rotationally symmetrical? |
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The L-arabinose operon, also called ara, is an operon required to break down the sugar L-arabinose in E. coli. This operon contains 3 structural genes in the following order, araB, araA, araD and expression is controlled by the product of a repressor called araC and the CAP protein which is regulated by cAMP in the same way as it is for the lactose operon.
Now Draw a schematic of what this operon might look like when glucose levels are low and arabinose levels are high. Include the relevant proteins and their effector molecules, the promoter, operator, and structural genes. Note if the operon is being transcribed or not.
The L-arabinose operon, also called ara, is an operon required to break down the sugar L-arabinose in E. coli. This operon contains 3 structural genes in the following order, araB, araA, araD and expression is controlled by the product of a repressor called araC and the CAP protein which is regulated by cAMP in the same way as it is for the lactose operon. From the available information here, draw a schematic of what this operon might look like when glucose levels are low and arabinose levels are high. Include the relevant proteins and their effector molecules, the promoter, operator, and structural genes.
Note if the operon is being transcribed or not.
The lactose operon in E. coli comprises two structural genes and three regulatory components.a.State the name of each structural gene and describe its function:
b.) State the name of each regulatory component and describe its function
Chapter 16 Solutions
Genetics: From Genes to Genomes
Ch. 16 - For each of the terms in the left column, choose...Ch. 16 - The following statement occurs early in this...Ch. 16 - One of the main lessons of this chapter is that...Ch. 16 - All mutations that abolish function of the Rho...Ch. 16 - The figure at the beginning of this chapter shows...Ch. 16 - The promoter of an operon is the site to which RNA...Ch. 16 - You are studying an operon containing three genes...Ch. 16 - You have isolated a protein that binds to DNA in...Ch. 16 - You have isolated two different mutants reg1 and...Ch. 16 - Bacteriophage , after infecting a cell, can...
Ch. 16 - Mutants were isolated in which the constitutive...Ch. 16 - Suppose you have six strains of E. coli. One is...Ch. 16 - The previous problem raises some interesting...Ch. 16 - For each of the E. coli strains containing the lac...Ch. 16 - For each of the following growth conditions, what...Ch. 16 - For each of the following mutant E. coli strains,...Ch. 16 - Maltose utilization in E. coli requires the...Ch. 16 - Seven E. coli mutants were isolated. The activity...Ch. 16 - Cells containing missense mutations in the crp...Ch. 16 - Six strains of E.coli mutants 16 that had one of...Ch. 16 - a. The original constitutive operator mutations in...Ch. 16 - In an effort to determine the location of an...Ch. 16 - Prob. 23PCh. 16 - The footprinting experiment described in Fig....Ch. 16 - Why is the trp attenuation mechanism unique to...Ch. 16 - a. How many ribosomes are required at a minimum...Ch. 16 - The following is a sequence of the leader region...Ch. 16 - For each of the E. coli strains that follow,...Ch. 16 - Prob. 29PCh. 16 - For each element in the list that follows,...Ch. 16 - Among the structurally simplest riboswitches are...Ch. 16 - Great variation exists in the mechanisms by which...Ch. 16 - Many genes whose expression is turned on by DNA...Ch. 16 - In 2005, Frederick Blattner and his colleagues...Ch. 16 - The E.coli MalT protein is a positive regulator of...Ch. 16 - Prob. 36PCh. 16 - Prob. 37PCh. 16 - Prob. 38PCh. 16 - Prob. 39PCh. 16 - Prob. 40PCh. 16 - Prob. 41PCh. 16 - The researchers who investigated bioluminescence...Ch. 16 - Prob. 43PCh. 16 - Quorum sensing controls the expression of...Ch. 16 - Scientists are currently screening a chemical...
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- A number of mutations affect the expression of the lac operon in E. coli. Consider each genotype below and complete the table using “+” to indicate that the gene is expressed, and “−” to indicate that gene is not expressed.arrow_forwardSupply the words “off" or “on" in the blanks below: In an inducible operon, transcription is normally and must be turned In a repressible operon, transcription is normally and must be turned Briefly describe the overall function of the structural genes in the lac operon. Briefly describe the overall function of the structural genes in the trp operon. For the following descriptions of the bacterial lac operon, determine if lactose is present (P) or absent (A). The repressor is bound to the operator. The repressor is inactive. RNA polymerase transcribes the structural genes. Allolactose is bound to the repressor For the following descriptions of the bacterial trp operon, determine if tryptophan levels are high (H) or low (L). The repressor is bound to the operator. The repressor is inactive. RNA polymerase transcribes the structural genes. Tryptophan is bound to the repressor.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. 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_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. Promoter || Operator genC genB gen operon Regulator genAarrow_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_forwardListed in parts a through g are some mutations that were found in the 5′ UTR of the trp operon of E. coli. What will the most likely effect of each of these mutations be on the transcription of the trp structural genes? a. A mutation that prevents the binding of the ribosome to the 5′ end of the mRNA 5′ UTR b. A mutation that changes the Trp codons in region 1 of the mRNA 5′ UTR into codons for alanine c. A mutation that creates a stop codon early in region 1 of the mRNA 5′ UTR d. Deletions in region 2 of the mRNA 5′ UTR e. Deletions in region 3 of the mRNA 5′ UTR f. Deletions in region 4 of the mRNA 5′ UTR g. Deletion of the string of adenine nucleotides that follows region 4 in the 5′ UTRarrow_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_forwardThe diagram below represents the tryptophan operon with the trp leader mRNA transcript enlarged to represent the AUG translation start codon, two consecutive tryptophan amino acid codons (UGGUGG), and 4 regions (1, 2, 3, and 4) that base pair to form different hairpin-loop structures in the MRNA leader region. Suppose a mutant bacteria has region 4 of the trp operon attenuator region mutated so that it cannot base pair normally. Would the bacteria grow in the absence of the amino acid tryptophan? (hint: in order for bacteria to grow in absence of tryptophan it should be able to synthesize its own tryptophan) Lead&r region trpE trpD trpC trpB trpA DNA 5' 3' Transcription trp leader sequence MRNA UGGUGG 1 (tryptophan codons) AUG UUUUUU No There is insutficient information to answer the question. O Yesarrow_forwardMutation in the regulatory gene in the lac operon results in the formation of an inactive repressor. List and explain the effect of such a mutation on the expression of the structural gene for lactose in E.coli?arrow_forward
- For each of the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor or as an inactive repressor. a. Negative control in a repressible operon b. Negative control in an inducible operonarrow_forwardThe diagram below represents a hypothetical operon in the bacterium E. coli. The operon consists of two structural genes (A and B), which code for the enzymes “Aase" and "Base", respectively, and also includes P (promoter) and O (operator) regions as shown. A В When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes "Aase" and "Base" are both synthesized at a 50-fold higher rate than in the absence of X. (X has a molecular weight of about 200.) Which of the following statements is true of the operon described above? The region of the A gene that codes for the carboxyl-terminal amino acid of “Aase" is near the left end of the A gene. The P region contains nucleotide sequences to which the RNA polymerase holoenzyme (including the o subunit) binds specifically but which the core enzyme does not recognize. The addition of X to the growth medium causes a repressor protein to bind tightly to the O region. The mRNA copied from this operon will be covalently…arrow_forwardGiven the Table below concerning the lac operon, match the letter with what would be occurring for each scenario. Repressor is bound to the operator, cAMP complex is bound and transcription is prevented. Allolactose is bound to the repressor, cAMP complex is bound, and transcription is prevalent. Allolactose is bound to the repressor, cAMP complex is not assembled, and transcription is slow Repressor is bound to the operator, cAMP complex is not assembled, and transcription is prevented.arrow_forward
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