Here is the Question ----->
--------------------------------------------------

"Mu" is a generalized transducing phage(i.e. similar to P1).
a derivative of MU was constructed that appears as follows.

        Mu                                      Mu
        left                                    right
        end     lacZ            bla(ampR)       end
       |----|-|--------|----|-----------|-----|----|
             |           |
             ^           ^
           no promoter   promoter

It's called Mu-lac and has the following properties:

properties1: Mu is a phage that can intergrate( ie. form a lysogen)
        at random sites in the genome of the host cell, E.coli. this property
        is determined by the sequences found in both ends of Mu. Thus, Mu-lac
        can also intergrate at random sites.
properties2: Following infectionss with Mu-lac phage, cell w/ Mu-lac integrate
        into their genome can selected by virtus of being virtue of being
        ampcillin resistant due to th presence of a bla gene w/ its own pro-
        mote.
properties3: The lacZ gene is intact and lacks only a promoter. Thus,B-galacto-
        sidase activity can only be expressed if Mu-lac insertion occurs
        downstream from an active promoter.

Questions are:

1: Devise a selection to isolate an E.coli cell that has a Mu-lac insertion
in araB gene. (u may begin w/ a cell containing any combination of lactose
mutations that u wish) It's will not b possible to do step 4 as a counter-
selection: u will have to do complementation. ASsume that u have a collection
of cells w/ F' factors containing the entire arabinose operon, including one
that r araA-. araB-. araC-, and araD-.

2: From araB- cells, devise a seleciton to isolate an e.coli cell that
expresses lacZ under control of the arabinose promoter, Pbad. (no needd do
step 3 and 4 in this selection)

3: Not alls araB- mutants isolated by the steps in question#1 will express lacZ
under the control of the arabinose promotor, Pbad. What is the main reason for this and what fraction of cells isolated in question#1 would u predict to be
in question#2

4: Give an argument Y the containing mutants of concern in question#1 would
in fact not have grown effectively in the selection u proposed in ur answer
to question#2..

-----------------------------------------------------

Any responses will be greatly appreciated,

have fun, guys....  :)

-bye-

--

HumanHunter  :->