Question

You prepare a gel mobility assay with the following samples:

Lane 1 Radiolabeled lacO DNA + Lac Repressor protein preincubated with allolactose
Lane 2 Radiolabeled lacO DNA + Lac Repressor protein preincubated with lactose
Lane 3 Radiolabeled lacO DNA + Lac Repressor protein missing its DNA binding domain
Lane 4 Radiolabeled lacO DNA + Lac super-repressor (Is) preincubated with allolactose
Lane 5 Radiolabeled lacO DNA + lac repressor protein

On which lanes do you expect to see two bands?

a. 3
b. Lane 1 and 2
c. Lane 2, 4, and 5
d. 2 and 4
e. 1 and 5

Answer 1

c. Lane 2, 4 and 5.

Step-by-step explanation:

Two bands will be seen when a fraction of DNA added to gel is bound by Lac repressor protein. Radiolabeled LacO DNA will have two bands. Lac repressor is encoded with lacl gene. It has binding ability due to allolactose formation.