Which plasmid feature enables selection of bacteria that have taken up the plasmid?

Which plasmid feature enables selection of bacteria that have taken up the plasmid?

• A. Ori
• B. Promoter
• C. Antibiotic resistance gene
• D. Multiple cloning site

Answer: (C)

Selecting bacteria that have taken up a plasmid hinges on a marker that lets those cells survive under specific conditions. The antibiotic resistance gene provides that survival advantage: cells carrying the plasmid express a protein that neutralizes or tolerates the antibiotic, so they grow on plates containing the antibiotic while cells without the plasmid are inhibited or die. The origin of replication ensures the plasmid is copied inside the cell, but it does not enable selection. A promoter directs transcription of genes, yet by itself it doesn’t distinguish plasmid-containing cells. The multiple cloning site is just a region for inserting DNA and does not confer survival.

Selecting bacteria that have taken up a plasmid hinges on a marker that lets those cells survive under specific conditions. The antibiotic resistance gene provides that survival advantage: cells carrying the plasmid express a protein that neutralizes or tolerates the antibiotic, so they grow on plates containing the antibiotic while cells without the plasmid are inhibited or die. The origin of replication ensures the plasmid is copied inside the cell, but it does not enable selection. A promoter directs transcription of genes, yet by itself it doesn’t distinguish plasmid-containing cells. The multiple cloning site is just a region for inserting DNA and does not confer survival.