Genetics: From Genes to Genomes, 5th edition
5th Edition
ISBN: 9780073525310
Author: Leland H. Hartwell, Michael L. Goldberg, Janice A. Fischer, Leroy Hood, Charles F. Aquadro
Publisher: McGraw-Hill Education
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Chapter 15, Problem 24P
For each of the E. coli strains that follow, indicate the effect of the genotype on the expression of the trpE and trpC genes in the presence or absence of tryptophan. (In the wild type [R+ P+ o+ att+ trpE+ trpC+], trpC and trpE are fully repressed in the presence of tryptophan and are fully induced in the absence of tryptophan.]
R = repressor gene; Rn product cannot bind tryptophan; R- product cannot bind operator
o = operator for the trp operon; o- cannot bind repressor
att = attenuator; att- is a deletion of the attenuator
P = promoter; P- is a deletion of the trp operon promoter
trpE− and trpC- are null (loss-of-function) mutations
| a. R+ P- o+ att+ trpE+ trpC+ |
| b. R- P+ o+ att+ trpE+ trpC+ |
| c. Rn P+ o+ att- trpE+ trpC+ |
| d. R- P+ o+ att- trpE+ trpC+ |
| e. R+ P+ o- att+ trpE+ trpC- /R- P+ o+ att+ trpE- trpC+ |
| f. R+ P- o+ att+ trpE+ trpC- /R- P+ o+ att+ trpE- trpC+ |
| g. R+ P+ o- att- trpE+ trpC- /R- P+ o- att+ trpE- trpC+ |
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For the lac genotypes shown in the following table, predict whether the structural genes (Z) are constitutive, permanently repressed, or inducible in the presence of lactose. Genotype Constitutive Repressed Inducible I+O+Z+ * I-O+Z+ I-OCZ+ I-OCZ+/F=O+ I+OCZ+/F=O+ ISO+Z+ ISO+Z+/F=I+
The lac genotypes are as shown below:
P+OcZ-Y+A+// P¯O+Z+Y+A+
(i)
The lac operon consists of three structural genes, lacZ, lacY and lacA. Which
structural genes are involved in lactose metabolism? Explain.
(ii)
Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote.
(iii)
What is the function of the promoter in the bacterial operon?
For the given genotypes (associated with the lac operon in E. coli), indicate with a "+" or "-" whether functional B - galactosidase would be expected to be produced in the indicated conditions, assuming low glucose levels.
B - galactosidase production
Genotype No lactose With lactose
a) I- O+ Z+ / F' I+ O+ Z+
b) IS O+ Z+/ F' I+ O+ Z+
Chapter 15 Solutions
Genetics: From Genes to Genomes, 5th edition
Ch. 15 - For each of the terms in the left column, choose...Ch. 15 - The following statement occurs early in this...Ch. 15 - One of the main lessons of this chapter is that...Ch. 15 - All mutations that abolish function of the Rho...Ch. 15 - The promoter of an operon is the site to which RNA...Ch. 15 - You are studying an operon containing three genes...Ch. 15 - Prob. 7PCh. 15 - You have isolated two different mutants reg1 and...Ch. 15 - Bacteriophage , after infecting a cell, can...Ch. 15 - Mutants were isolated in which the constitutive...
Ch. 15 - For each of the E. coli strains containing the lac...Ch. 15 - For each of the growth conditions listed, what...Ch. 15 - For each of the following mutant E. coli strains,...Ch. 15 - Maltose utilization in E. coli requires the...Ch. 15 - Seven E. coli mutants were isolated. The activity...Ch. 15 - Prob. 16PCh. 15 - Six strains of E.coli mutants 16 that had one of...Ch. 15 - a. The original constitutive operator mutations in...Ch. 15 - Prob. 19PCh. 15 - Figure 15.16 on p. 525 shows that in the lac...Ch. 15 - Why is the trp attenuation mechanism unique to...Ch. 15 - a. How many ribosomes are required at a minimum...Ch. 15 - The following is a sequence of the leader region...Ch. 15 - For each of the E. coli strains that follow,...Ch. 15 - One mechanism by which antisense RNAs act as...Ch. 15 - For each element in the list that follows,...Ch. 15 - Great variation exists in the mechanisms by which...Ch. 15 - Many genes whose expression is turned on by DNA...Ch. 15 - Prob. 29PCh. 15 - The E.coli MalT protein is a positive regulator of...Ch. 15 - Prob. 31PCh. 15 - To find genes that are turned on or off in...Ch. 15 - Prob. 33PCh. 15 - Prob. 34PCh. 15 - Prob. 35PCh. 15 - The researchers who investigated bioluminescence...Ch. 15 - Prob. 37PCh. 15 - Quorum sensing controls the expression of...
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- For the lac genotypes of Escherichia coli shown in the following Table 1, predict the expression of beta-galactosidase (Z) and permease (Y) is inducible or noninducible or constitutive. Explain your answer. Table 1 Genotype I-P+O+Z+Y+ (i) (ii) I+P+OCZ+Y+ (iii) ISP+O+Z+Y+ (iv) I+P+O+Z+Y-//I+P-O+Z+Y+ (v) ISP+OcZ+Y+//I-P+O+Z+Y- Condition No lactose No lactose lactose lactose No lactosearrow_forwardIn the galactose operon of Escherichia coli, a repressor, encoded by the galR gene, binds to an operator site, galo, to regulate the expression of three structural genes, galE, galT, and galK. Expression is induced by the presence of galactose in the media. For each of the strains listed, would the cell show constitutive, inducible, or no expression of each of the structural genes? (Assume that galR−is a loss-of-function mutation.) galR− galo+ galE+ galT+ galK+ galR+ galoc galE+ galT+ galK+ galR− galo+ galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+ galR− galoc galE+ galT+ galK−/ galR+ galo+ galE− galT+ galK+arrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the lowest beta-galactosidase enzyme activity, when grown in the lactose medium. OF POZY Ort Ptot Z¹ Yt Ort p²o+z¹Y+ Orpt ot ztyarrow_forward
- A number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the lowest beta-galactosidase enzyme activity, when grown in the lactose medium. Orpt o* z* r* Orpt ot z* Y OrptoztY Orrotzr OrPotz*Yarrow_forwardA number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the highest beta-galactosidase enzyme activity, when grown in the lactose medium. O CAP+ r* p* o* z O CAP* I P* o* z* O CAP* r* P O* z* O CAP I P* O z*arrow_forwardSuppose you have six strains of E. coli. One is wildtype, and each of the other five has a single one of thefollowing mutations: lacZ−, lacY−, lacI−, oc, andlacIS. For each of these six strains, describe thephenotype you would observe using the following assays. [Notes: (1) IPTG is a colorless synthetic molecule that acts as an inducer of lac operon expressionbut cannot serve as a carbon source for bacterialgrowth because it cannot be cleaved byβ-galactosidase; (2) X-gal cannot serve as a carbonsource for growth; (3) E. coli requires active lactosepermease (the product of lacY) to allow lactose,X-gal, or IPTG into the cells.] Colony color in medium containing glycerol as theonly carbon source and X-gal, but no IPTG.d. Colony color in medium containing high levels ofglucose as the only carbon source, X-gal, andIPTG.e. Colony color in medium containing high levels ofglucose as the only carbon source and X-gal, butno IPTGarrow_forward
- For each of the E. coli strains containing lac operon alleles listed, indicate whether the strain is inducible, constitutive, or unable to express beta-galactosidase and permease. (P+ and P- are functional and nonfunctional promoters, respectively) I+ P+ o+ Z- Y+ / I+ P+ oc Z+ Y+ I+ P+ o+ Z+ Y+ / I- P+ oc Z+ Y- I+ P+ o+ Z- Y+ / I- P+ oc Z+ Y- I- P- o+ Z+ Y- / I+ P+ oc Z- Y+ IS P+ o+ Z+ Y+ / I- P+ o+ Z+ Y-arrow_forwardThe inducible galactose operon of E. coli has three co-transcribed genes (galK, galE, galT) encoding the kinase enzyme, epimerase enzyme, and transferase enzyme, respectively. You have isolated an interesting regulatory mutant, galX, with the phenotype shown in the second row of the following table. A means enzyme absent; P means enzyme present. without galactose with galactose genotype kinase transferase kinase transferase wildtype A A P P galx P P P P What is the role of the galX gene? [Select] The phenotype of a galX¯ mutant is an example of [ [ Select] To determine if the galX gene encodes a regulatory protein or serves as a regulatory site, you make a partial diploid with the following genotype: galX galK+ galT¯ / galX* galK¯ galT+ Complete the table below by assigning to each number in blue either A or P to indicate the enzyme phenotype expected if galX encodes a protein or serves as a site. without galactose with galactose kinase transferase as site 1 2 as protein 5 6 1 [ Select…arrow_forwardA strain of E. coli has the genotypes shown below at the lac operon, where I = regulator gene, P = promoter, O = operator, Z = βgalactosidase gene, and Y = permease gene. The superscript+ indicates a wild-type allele,c indicates a constitutive mutation, and− indicates a defective mutation. For each genotype, indicate whether the enzyme will be synthesized or not synthesized when lactose is present or absent by placing a + for synthesis occurring and a − for synthesis not occurring in the appropriate blank. Explain your reasoning for each answer.arrow_forward
- Why is it adaptive for the structural genes for using lactose to be under the control of a single promoter (i.e., synthesize a polycistronic message rather than three monocistronic messages)? a. For efficient absorption and catabolism of lactose, structural genes send a single signal. This is why polycistronic message is favored more than the monocistronic message since the former involves transmission of numerous messages in initiation and termination. b. Polycistronic message is favored more than the monocistronic message. c. Polycistronic message is favored more than the monocistronic message since the former involves transmission of numerous messages in initiation and termination. d. For an efficient absorption and catabolism of lactose, structural genes send a single signal only. e. Polycistronic message is favored more than the monocistronic message since the former involves transmission of single message in initiation and termination.arrow_forwardI have this strain of e coli. Is P+ o+ Z+ Y+ / I- P+ oC Z- Y+ Will beta-galactosidase and permease be expressed? If they are will they be inducible or constitutive?arrow_forwardThe following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/). The possible answers indicate with a ʺ+ʺ or a ʺ-ʺ whether β-galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)Genotype F: I+ Oc Z-/ Fʹ I- O+ Z+ KEY:I+ = wild-type repressorI- = mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+ = wild-type operatorOc = constitutive operator (insensitive to repressor)arrow_forward
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