Problem) For each of the following partial diploids indicate whether enzyme synt

Question

Problem) For each of the following partial diploids indicate whether enzyme synthesis is constitutive or inducible.

Answer is given below could you explain how to get the solution? how do you determine if the enzyme synthesis is constitutive or inducible for partial dipolids

(a)     I+O+Z+Y+/I+O+Z+Y+ (its hard to see, power signs are ++++/++++)

        Inducible

(b)    I+O+Z+Y+/I+OcZ+Y+    (++++/+c++)

          Constitutive

(c)    I-OcZ+Y+/I+O+Z+Y+     (-c++/++++)

         Constitutive

(d)    I+O+Z+Y+/I-O+Z+Y+ (++++/-+++)

          Inducible

(e)    I-OcZ+Y+/IsO+Z+Y+    (-c++/s+++)

          Constitutive

Explanation / Answer

Answers:

(a)     I+O+Z+Y+/I+O+Z+Y+ (++++/++++)

        Inducible system because of the presence of wild type genotype and phenotype.

(b)    I+O+Z+Y+/I+OcZ+Y+    (++++/+c++)

Constitutive system because Oc mutation produces an operator that is not recognized by the lac repressor.

(c)    I-OcZ+Y+/I+O+Z+Y+     (-c++/++++)

         Constitutive system because Oc mutation produces an operator that is not recognized by the lac repressor.

(d)    I+O+Z+Y+/I-O+Z+Y+ (++++/-+++)

          Inducible system because I+ is dominant to I-.

(e)    I-OcZ+Y+/IsO+Z+Y+    (-c++/s+++)

          Constitutive system because IS mutant repressor cannot bind to OC (Since OC mutation is epistatic to IS mutation.

Note: An I+O+Z+Y+ / I+OcZ+Y+ (option b) partial diploid would exhibit constitutive synthesis of b-galactosidase and b-galactoside permease, whereas an I+O+Z+Y+ / I-O+Z+Y+ (option d) partial diploid would be inducible for the synthesis of these enzymes.

IS = Super repressor

I+ = Inducible

I- = Constitutive

Oc = Constitutive, Cis dominant

O+ = Inducible, Cis dominant

Z+Y+ = Structural genes

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