Problem For each of the following partial diploids indicate

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⁺O^cZ⁺Y⁺    (++++/+c++)

          Constitutive

(c)    I^-O^cZ⁺Y⁺/I⁺O⁺Z⁺Y⁺     (-c++/++++)

         Constitutive

(d)    I⁺O⁺Z⁺Y⁺/I^-O⁺Z⁺Y⁺ (++++/-+++)

          Inducible

(e)    I^-O^cZ⁺Y⁺/I^sO⁺Z⁺Y⁺    (-c++/s+++)

          Constitutive

Solution

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 O^c mutation produces an operator that is not recognized by the lac repressor.

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

         Constitutive system because O^c 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 I^S mutant repressor cannot bind to O^C (Since O^C mutation is epistatic to I^S mutation.

Note: An I⁺O⁺Z⁺Y⁺ / I⁺O^cZ⁺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.

I^S = Super repressor

I⁺ = Inducible

I^- = Constitutive

O^c = Constitutive, Cis dominant

O⁺ = Inducible, Cis dominant

Z⁺Y⁺ = Structural genes