Question

You have isolated a DNA fragment containing a human gene involved in lung cancer and are working inserting it into a standard plasmid vector used in molecular cloning which has a multiple cloning site in the lacZ gene. After cutting the DNA fragment and the vector with the same restriction enzyme and ligating the cut DNA, you transform bacteria with hopefully the recombinant vector. How do you expect to identify bacteria with the recombinant vector?
A. Bacteria with the recombinant vector will be resistant to antibiotic treatment and form blue colonies in the presenceof X-gal.
B. Bacteria with the recombinant vector will be resistant to antibiotic treatment and form white colonies in the presenceof X-gal.
C. Bacteria with the recombinant vector will be sensitive to antibiotic treatment and form blue colonies in the presenceof X-gal.
D. Bacteria with the recombinant vector will be sensitive to antibiotic treatment and form white colonies in the presenceof X-gal.
E. None of these are correct.

Answer 1

Answer:

Option

Explanation:

Beta-galactosidase is a protein encoded by the lacZ gene and the process of alpha complementation is used in identifying the vector recombinant,

The insertion of the target DNA fragment into a vector; whose inactive beta galctosidase has been made functional by adding an alpha peptide will disrupt the complementation process and then render the protein non-functional such that the transformed bacteria cells becomes sensitive to antibiotic treatment and then proceed to form white colonies in the presence of X-gal. While cells that have plasmids with DNA inserts will remain resistant and form blue colonies in the presence of X-gal.