Plasmid antibiotic resistance as a selectable marker
After transforming bacteria with a plasmid carrying an ampicillin resistance gene, researchers grow them on ampicillin plates. Why?
Answer C: explanation for every choice
A
Ampicillin kills cells. It does not help them take up DNA.
B
Expression of the inserted gene depends on its promoter, not on the antibiotic.
C
Correct. The resistance gene is a selectable marker: untransformed bacteria die.
D
Bacteria with the plasmid are the ones that resist ampicillin.
TakeawayAntibiotic resistance genes select for transformed cells.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb51.