Alpha complementation is an indicator of lacZ system. Which of the statement is incorrect for it?

A. One portion of the lacZ gene known as minigene is present in the plasmid

B. Another portion is present in the host itself

C. If they both are allowed to combine in the presence of IPTG, X-gal, and ampicillin, blue colonies are observed

D. If an insert is also present along with the host and plasmid, it results in the formation of blue colonies

Explanation: Alpha complementation system is used as a lacZ indicator system. In this, one portion of the lacZ gene is present in the plasmid and is termed minigene. The other portion is present in the host itself. The combining of two portions is very important to have an intact lacZ gene and in this case, it is intact blue colonies are observed in the presence of IPTG, ampicillin, and X-gal. It is so because lacZ breaks down X-gal and it gives blue color. If the insert is also there, the lacZ gene is interrupted and thus X-gal is not broken down and hence white colonies are obtained.