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For an E. coli strain with the
a. Growth medium contains lactose and glucose.
b. Growth medium contains glucose and no lactose.
c. Growth medium contains lactose and no glucose.
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Chapter 12 Solutions
Genetic Analysis: An Integrated Approach Plus Mastering Genetics with Pearson eText -- Access Card Package (3rd Edition) (What's New in Genetics)
- The 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_forwardThe following table lists 4 bacterial strains that are partial diploids for lac operon genes. Given the activity of beta-galactosidase measured for each strain in the absence (-lac) or presence (+lac) of lactose, complete the table by choosing the appropriate symbol (+, -, C, S) to indicate the allele of the gene or site missing from the table (blue numbers). + = wildtype, - = null mutation, c = constitutive, s =super repressor chromosome plasmid B-gal act. strain 10 Z A 1 C B 3 4 + C + 6 D 9 + 1 [Select] 3 [Select] 5 [Select] 7 [ Select] 9 [Select] | 0 2 + + 5 + 7 10 Z + -lac +lac 0.062 0.058 0.003 0.004 0.062 0.117 0.003 0.060 + 8 + 2 [Select] 4 [Select] 6 [Select] 8 [Select] 10 [Select]arrow_forwardFor 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+arrow_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. OF POZY Ort Ptot Z¹ Yt Ort p²o+z¹Y+ Orpt ot ztyarrow_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_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
- If a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??arrow_forwardGiven the following genotypes, explain, by answering the questions in each number, how the mutation (identified by a (-) superscript) will affect E. coli grown in lactose medium. Will there be a complete set ofgene products? (Yes/No) Will the lac operon be turnedon/off? Will the cell survive? (Yes/No) a. i + p + o + z - y + b. i + p - o + z + y + c. i + p + o - z + y +arrow_forwardIf a wild-type (normal, NOTmutated) E. coli strain is grown in a medium: a. without lactose or glucose, how many proteins (and which ones) are bound to the lac operon? b. Without lactose, but with glucose, how many proteins (and which ones) are bound to the lac operon??- lac repressorarrow_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_forwardConsider this strain of E. coli with lac operon alleles: IS pt o* z* y+ /T p* oCz- Y+ In a written response, briefly explain if beta-galactosidase AND permease will be expressed, and if so, will they be inducible or constitutive.arrow_forwardFor the following genotypes of E. coli strains, state whetherenzyme activity is inducible (I), constitutive (C), or uninducible (U).Key to symbols in table:z = structural gene for -galactosidasey = structural gene for permeasea = structural gene for transacetylasep = promoter (for lac operon)i = structural gene for the lac repressor (regulator gene)o = operator (binding site for repressor)Genotype -gal (z) Permease (y) Transacetylase (a)i+ p+ oC z- y- a+i- p+ o+ z+ y- a- /i+ p- oc z- y+ a-i- p+ o+ z+ y- a+ /i+ p+ oc z- y+ a-i+ p+ o+ z- y- a+i- p- o+ z+ y- a+ /i- p+ o+ z- y+ a-iS p+ o+ z- y- a+i- p+ o+ z+ y- a+ /i+ p- oc z- y+ a-is p+ o+ z- y+ a+ /i+ p+ oc z+ y- a-i- p- o+ z+ y- a+ /i- p+ o+ z- y- a-is p+ oc z+ y- a+i+ p+ oc z+ y- a+arrow_forward
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