Question

You are working in a molecular biology lab and, unbeknownst to you, your lab partner left the foreign genomic DNA you are planning to clone on the lab bench overnight instead of storing it in the freezer. As a result, it was degraded by nucleases, but still used in the experiment. The plasmid, on the other hand, is fine. What results would you expect from your molecular cloning experiment?
A. There will be no colonies on the bacterial plate.
B. There will be blue colonies only.
C. There will be blue and white colonies.
D. The will be white colonies only.

Answer 1

Answer:

B There will be blue colonies only

Explanation:

This screen in called the blue white screening.  This is a rapid test that allows scientist to check for their insert of choice in the colonies at a glance. The concept is that where the insert is located the lac Z gene in the vector is interrupted and therefor Xgal, a reporter can be produced. Where there are blue colonies being formed the plasmid has self-ligated and the lac Z gene is not interrupted and the X-gal can be formed rendering a blue color.