35 The initial studies on gene regulation were conducted on the tau sperce giest
ID: 182473 • Letter: 3
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35 The initial studies on gene regulation were conducted on the tau sperce giesta but genes for different loci can be introduced to gencrate orgatisms that anc ad tobe dlws E. coli to grow in the presence of lactose but in the abncace of plecine The lactoseents data of gene expression from the lactose operón in E.col cells carrying two copies the epere re endcated mutations. A"+"sign indicates that beta-galactosidase, the product of operon a tale is needed for lactose catabolism is expressed. The experiments were carried out in the arsence of plucise lacz gene, which Match the following genotypes in the first table to the corresponding phenotypes in the second P is the promoter I is the repressor gene O is the operator sequence Z is the lacZ gene tihle. Genotypes table Answer Genotype Choice A) B) IP.OZ. /rp.O.Z' 1.P..Z' /I"P.OcZ' C) Phenotypes table Question Number Lacz expression LacZ expression in in the absence the presence of of lactose lactose 34 35.Explanation / Answer
A. I-P+O+Z+I+P+O+Z+
This matches with 35. This operon will behave like any other normal operon because the gene that is absent codes for a repressor molecule that acts in a trans manner i.e. the functional repressor molecule can bind the operator of the operon whose "I" gene is deleted.
B. I+P-O+Z+I+P-O+Z+
This matches with 34. This is because the promoter would not bind the RNA polymerase and thus the operon wont be expressed in any condition i.e. the operon will be repressed in absence and in presence of lactose.
C. I+P+O+Z+I+P+OcZ+
This matches with 33. The operator carries a constitutive mutation denoted by C which means the even if the repressor binds the operator it doesnt inhibit the operon and the operon is expressed in all conditions, presence or absence of lactose.
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