Concept explainers
Identify which of the following lac operon haploid genotypes transcribe operon genes induciblyand which transcribe genes constitutively. Indicate whether the strain is
a.
b.
c.
d.
e.
f.
g.
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- Give all possible genotypes of a lac operon that produces, or fails to produce, β-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose absent Lactose present β-Galactosidase Permease β-Galactosidase Permease a. − − + + b. − − − + c. − − + − d. + + + + e. − − − − f. + − + − g. − + − +arrow_forwardGive all possible genotypes of a lac operon that produces, or fails to produce, B-galactosidase and permease under the following conditions. Do not give partial-diploid genotypes. Lactose present B-Galactosidase Lactose absent B-Galactosidase Permease Permease a. b. C. d. e. f. g. + I + II + + + | +Iarrow_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. Orpt o* z* r* Orpt ot z* Y OrptoztY Orrotzr OrPotz*Yarrow_forward
- 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+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_forwardStrain 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. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lac operon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.arrow_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_forwardThe map of the lac operon is shown below. Consider the following examples that include both haploids and partial diploids and explain in each scenario whether the repressor can bind and regulate expression and whether or not the lac operon is expressed. For partial diploids the plasmid is indicated by the F’. I+ O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ / F’ I+ O+ Z+ Y+ I- O+ Z+ Y+ I+ Oc Z+ Y+arrow_forwardThe streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forward
- Suppose 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_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. Circle the least number of components for an F' plasmid that will restore normal regulation and function of the lacoperon in the resulting partial diploid. (may need more than one) (a) lacI+ (b) lacO+ (c) lacP+ (d) lacZ+ (e) None, cannot be restored.arrow_forward
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