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NEET2026BiologyChapterActual

In a typical cloning vector such as pBR322, what is the primary function of the genes encoding resistance to antibiotics like ampicillin or tetracycline?

Options

  1. AThey act as the origin of replication ( ori ) to initiate DNA synthesis.
  2. BThey serve as selectable markers to help identify and isolate transformants.
  3. CThey provide the primary mechanism to cut the host genomic DNA.
  4. DThey code for proteins that are essential for the replication of the plasmid.

Correct answer

B. They serve as selectable markers to help identify and isolate transformants.

Step-by-step solution

In a cloning vector like pBR322, genes encoding resistance to antibiotics (such as ampicillin or tetracycline) function as selectable markers. Selectable markers are essential for identifying and eliminating non-transformants and selectively permitting the growth of transformants. When host cells are plated on a medium containing the specific antibiotic, only those cells that have successfully taken up the plasmid (transformants) will survive and form colonies, while the non-transformants will be killed. Answer: Th

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