Question

1) Figure out which of the following things below represents Lac I, Lac O, Lac promoter, or Lac Z. Explain your reasoning, and cite the genetic strains that were necessary to reach your conclusion.

Y = permease

                                       b-Galactosidase Activity      Permease Activity

   Genotype                              -lac      +lac                 -lac          +lac

1. a⁺b⁺c⁺ d⁺                                                -            +                      -                 +

2. a^-b⁺c⁺ d⁺                                                 -            -                      -                 +

3. a⁺b^-c⁺ d⁺                                                 +           +                      +                +

4. a⁺b⁺c^- d⁺                                                 -            -                      -                 -

5. a⁺b⁺c⁺ d^-                                                 +           +                      +                +

6. a⁺b⁺c^- d⁺ Y^-/ a^-b⁺c⁺ d⁺ Y⁺            -            -                      -                 +

7. a⁺b⁺c⁺ d⁺ Y^-/ a^-b⁺c^- d⁺ Y⁺           -            +                      -                 -

8. a⁺b^-c⁺ d⁺ Y^-/a^-b⁺c⁺ d⁺ Y⁺            -            +                      -                 +

9. a⁺b⁺c⁺ d⁺ Y^-/a^-b^-c⁺ d⁺ Y⁺            -            +                      -                 +

10. a⁺b⁺c⁺ d^- Y^-/a^-b⁺c⁺ d⁺ Y⁺         +           +                      -                 +

11. a⁺b⁺c⁺ d⁺ Y^-/a^-b⁺c⁺ d^- Y⁺         -            +                      +                +

Answer 1

b = lac i

a = lac z

c = Lac promoter

d = operator

                        

	beta galactosidase activity lac- lac +	Permease Activity lac- lac +	explanation
a-b+c+ d+	-            -	- +	a is lac z because even in the presence of lactose beta galactosidase activity is absence
a+b-c+ d+	+           +	+ +	b is lac I because it get mutated then it will not able to bind to the operator thus even in the absence of lactose the lac operon will be active and have beta galactosidase and permease activity
a+b+c- d+	- -	- -	c is promoter because if c get mutated then no matters what beta galactosidase and permease activity will be not there even in the presence of lactose
a+b+c+ d- Y-/ a-b+c+ d+ Y+	+           +	- +	d is Lac O operator MUTANT OF D will not able to get bind with repressor thus activation of beta Galactosidase even in the ABSENCE of lactose will occur but lac O is cis acting element thus if y is permease and y - will not form permease (IN CASE OF BLACK BOLD STRAND ) while in the case of strand y + is their so permease will form in the presence of lactose ( IN CASE OF RED HIGHLIGHTED STRAND )

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