- For developing transgenic mice, embryonic stem cells are engineered to express the transgene. These cells are selected by
(1) novobiocin. (2) neomycin.
(3) tetracycline. (4) penicillin.The correct answer is (2) neomycin.
Option-wise explanation
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(1) Novobiocin
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An inhibitor of DNA gyrase, used mainly as an antibacterial drug and sometimes in bacterial selection.
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It is not the classical selectable marker antibiotic for mammalian ES cells in transgenic mouse protocols.
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(2) Neomycin – correct
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Transgenic constructs for ES cells typically carry the neor (neo) gene, which confers resistance to neomycin analog G418.
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After introducing the construct, ES cells are grown in medium containing G418; only cells that have integrated the transgene with neor survive, allowing selection of correctly modified clones.
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(3) Tetracycline
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Widely used in bacteria and in tetracycline‑regulated expression systems, but not the standard selection drug for ES cells during generation of transgenic mice.
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Tet systems usually use Tet as a regulator, not as the primary kill‑or‑survive selection agent.
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(4) Penicillin
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Primarily an antibacterial agent added to mammalian cultures to prevent contamination.
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It does not serve as a selective agent for transfected ES cells in transgenic mouse production.
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Therefore, for selecting embryonic stem cells engineered to express a transgene when developing transgenic mice, the commonly used antibiotic is neomycin (G418), making option (2) correct.
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