Question

In genetic engineering antibiotics are used

• A. as selectable markers
• B. to select healthy vectors
• C. as sequences from where replication starts
• D. to keep the cultures free of infection.

Answer 1

The correct option is A as selectable markers

Selectable markers are those genes that help in selecting those host cells which contain vectors (i.e., transformants) and eliminating the non-transformants. The genes encoding resistance to antibiotics such as tetracycline, ampicillin, kanamycin etc., are useful selectable markers for E.coli. Plasmid pBR322 has two resistance genes – ampicillin resistance $\left(am{p}^r\right)$ and tetracycline resistance $\left(te{t}^r\right)$ which are considered useful for selectable markers.