If two plasmids with different antibiotic resistance genes are mixed, how should you handle sorting?

If two plasmids with different antibiotic resistance genes are mixed, how should you handle sorting?

• A. Treat both with both antibiotics
• B. Divide into two batches; treat each with one antibiotic
• C. Use different temperatures
• D. Ignore antibiotic selection

Answer: (B)

When you have two plasmids that each carry a different antibiotic resistance, you need to apply selective pressure specific to each plasmid. Dividing the culture into two batches and treating each with the antibiotic corresponding to one resistance gene allows you to selectively grow cells carrying that particular plasmid. This separation makes it possible to sort or identify the two populations based on which antibiotic they survive in. Treating both cultures with both antibiotics would only allow cells that have both plasmids to survive, which defeats the goal of separating them. Using different temperatures does not create the necessary selection for antibiotic resistance, and ignoring antibiotic selection would let cells lose the plasmids over time and grow non-transformed cells.

When you have two plasmids that each carry a different antibiotic resistance, you need to apply selective pressure specific to each plasmid. Dividing the culture into two batches and treating each with the antibiotic corresponding to one resistance gene allows you to selectively grow cells carrying that particular plasmid. This separation makes it possible to sort or identify the two populations based on which antibiotic they survive in.

Treating both cultures with both antibiotics would only allow cells that have both plasmids to survive, which defeats the goal of separating them. Using different temperatures does not create the necessary selection for antibiotic resistance, and ignoring antibiotic selection would let cells lose the plasmids over time and grow non-transformed cells.