3 ms·

Interesting. I have a question, why not pair Gene A with something still detectable but less "dangerous", like a gene that change body color, or emit different

Interesting. I have a question, why not pair Gene A with something still detectable but less "dangerous", like a gene that change body color, or emit different color under UV light. Sorry i am totally noob here

fabian2k 1y ago
Because the antibiotic automatically selects the successful clones. The others that didn't incorporate the plasmid don't grow into colonies. Without antibiotics your plate will be entirely full of bacteria, you can't pick individual clones from that. And you want clones, so all identical bacteria derived from a single successful integration of your plasmid into a bacterium. You don't want a mixture of bacteria with different DNA. This process isn't perfect and you need to screen out cases where your DNA sequence is not correct. And by far the easiest way to do that is to grow on plates with antibiotics, and an amount of bacteria that results in a few individual colonies, with each clone being full of genetically identical bacteria. You generally want antibiotics in your media anyway, working without antibiotics makes it much more difficult. You don't have 100% perfectly sterile conditions, with antibiotics you have a much larger margin here.
solid_fuel 1y ago
Just to elaborate a bit more, the problem is that even a colony which, for example, glows under a blue light, will have some members that didn't uptake the genes. So you need a more proactive filtering method. There's also the fact that bacteria tend to lose non-adaptive traits pretty quickly once the selection pressure is gone, so having the antibiotic resistance attached to your gene of interest makes it much more likely to stick around for the duration. Additionally, as others have said, this particular antibiotic (from the post) isn't even used for human treatment so it's not really particularly more "dangerous", we just tend to get nervous around anything "antibiotic resistant" because we jump to thinking about like, MRSA.
sjducb 1y ago
Best case you’re transforming 10^6 cells and you expect 20 of them to take up the DNA. Worse case it could be 10^11 cells for a strain of bacteria that doesn’t transform well. You would have to look at a lot of colonies to find the one that transformed.

fabian2k 1y ago

Because the antibiotic automatically selects the successful clones. The others that didn't incorporate the plasmid don't grow into colonies. Without antibiotics your plate will be entirely full of bacteria, you can't pick individual clones from that. And you want clones, so all identical bacteria derived from a single successful integration of your plasmid into a bacterium. You don't want a mixture of bacteria with different DNA. This process isn't perfect and you need to screen out cases where your DNA sequence is not correct. And by far the easiest way to do that is to grow on plates with antibiotics, and an amount of bacteria that results in a few individual colonies, with each clone being full of genetically identical bacteria. You generally want antibiotics in your media anyway, working without antibiotics makes it much more difficult. You don't have 100% perfectly sterile conditions, with antibiotics you have a much larger margin here.

solid_fuel 1y ago

Just to elaborate a bit more, the problem is that even a colony which, for example, glows under a blue light, will have some members that didn't uptake the genes. So you need a more proactive filtering method. There's also the fact that bacteria tend to lose non-adaptive traits pretty quickly once the selection pressure is gone, so having the antibiotic resistance attached to your gene of interest makes it much more likely to stick around for the duration. Additionally, as others have said, this particular antibiotic (from the post) isn't even used for human treatment so it's not really particularly more "dangerous", we just tend to get nervous around anything "antibiotic resistant" because we jump to thinking about like, MRSA.

sjducb 1y ago

Best case you’re transforming 10^6 cells and you expect 20 of them to take up the DNA. Worse case it could be 10^11 cells for a strain of bacteria that doesn’t transform well. You would have to look at a lot of colonies to find the one that transformed.