For the following lac genotypes, predict whether the structural genes (Z) are constitutive, permanently repressed, or inducible in the presence of lactose. Genotype Constitutive Repressed Inducible I+P+O+Z+ I-P+O+Z+ I+P+OCZ+ I+P-O+Z+ IS P+O+Z+ F'I+ / I+P+O+Z+ F'OC / IS P+O+Z+ IS P+O+Z+ / F'I+
Added by Tracy K.
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I+P+O+Z+: This is the wild type genotype. The structural genes are inducible in the presence of lactose. Show more…
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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.
Sri K.
Groups of alleles associated with the lactose operon are as follows (in order of dominance for each allelic series): repressor, $I^{s}$ (superrepressor), $I^{+}$ (inducible), and $I^{-}(\text {constitutive }) ;$ operator, $O^{c}$ (constitutive, $c i s^{-}$ dominant) and $O^{+}$ (inducible, cis-dominant); structural, $Z^{+}$ and $Y^{+}$ (a) Which of the following genotypes will produce (a) Which of the following genotypes will produce \beta-galactosidase and $\beta$ -galactoside permease if lactose is present: (1) $I^{+} O^{+} Z^{+} Y^{+},$ (2) $I^{-} O^{c} Z^{+} Y^{+},$ (3) $I^{s} O^{c} Z^{+} Y^{+}$ (4) $I^{s} O^{+} Z^{+} Y^{+}$, and (5)$I^{-} O^{+} Z^{+} Y^{+}$ ? (b) Which of the above genotypes will produce $\beta$ -galactosidase and $\beta$ -galactoside permease if lactose is absent? Why?
GENETICS, Thank You! For the lac operon in E. coli, I = lacI, the repressor gene, P = the lac promoter, O = the lac operator, Z = lacZ or the beta-galactosidase gene, Y = lacY, the permease gene. (+ = gene intact or functional; - = gene deleted or nonfunctional). Fill in the table below using a '+' to indicate the presence of the enzyme and '-' to indicate the absence of the enzyme. Although there is residual expression in the absence of lactose, please call this '-' since there is a thousand-fold increase in the presence of lactose. Genotype No Lactose Lactose Lac Z Lac Y Lac Z Lac Y I+P-O+Z+Y+ I+P+O+CZ+Y+ I+P+O+Z+Y- /F' I-P+O+Z-Y+ I-P+OcZ+Y+ /F' IsP+O+Z-Y- I+P+O+Z-Y+ /F' I-P+O+Z+Y-
Suman K.
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