Why antibiotic resistance gene is important in plasmid.
Answers
The whole point of an artificial plasmid is to insert it into bacteria to change their gene expression. Say you have a plasmid that has a gene for making insulin. You inject it into a culture of bacteria and let them take it up.
A few hours later, you get some bacteria producing insulin for you, but most of the bacteria in your culture haven’t taken up the plasmid, so they’re not doing anything useful. If anything, they’re competing with your insulin-producing bacteria for nutrients. So you decide to kill them with antibiotics.
Well, it works. You’ve killed off the useless bacteria. Except oops, you’ve also killed the bacteria that were being useful.
But if you include an antibiotic resistance gene in the plasmid, then any bacteria that take up the plasmid will produce insulin and survive when you kill off the useless ones, so that you’re only left with insulin-producing bacteria.