A gene, whose expression helps to identify transformed cells is known as

1. selectable marker                 

2. vector

3. plasmid                                 

4. structural gene

Bacterial colonies that have a foreign DNA fragment inserted into the plasmid will appear white because-

1.  X-gal can be cleaved by $\beta$-galactosidase

2.  Lac-Z gene shows insertional inactivation due to insertion of foreign DNA

3.  Lac-Z gene is active

4.  X-gal can be cleaved by permease

A selectable marker is used to:

How are transformants selected from nontransformants?

1. Presence of more than one recognition site in the vector DNA.

2. Presence of alien DNA into the vector DNA results into insertional inactivation of selectable marker.

3. Antibiotic resistance gene gets inactivated due to insertion of alien DNA.

4. Both 2 and 3.

In genetic engineering, the antibiotic-resistance gene is used:
1.  To select healthy vectors
2.  As sequences from where replication starts
3.  To keep the cultures free of infection
4.  As selectable markers

Insertional inactivation of a gene helps in
a. Identification of recombinant clones
b. Identification of deletion mutants
c. Identification of recombinant transformants
d. Elimination of suppression mutants

Which of the following would you choose as the safest and least cumbersome selectable marker-

Insertional inactivation of the lac Z gene forms-

In the screening process during rDNA experiments, clones that metabolize $\beta$-gal turn:

1. Colorless

2. Blue

3. Yellow

4. Green

Why is a marker gene useful?

1. It shows you whether the gene being added, has been taken up or not.

2. It's a way of labelling which gene you want to modify.

3. It sticks with the striker gene.

4.  It marks the position of r-DNA