A foreign gene was ligated into the BamHI site of the tetR gene of pBR322…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A foreign gene was ligated into the BamHI site of the tetR gene of pBR322. The plasmids were put into bacteria. colonies grew on a plate with ampicillin. The colonies were copied onto a plate with tetracycline, and of them grew there.
- How many colonies carry a plasmid with the foreign gene?
- What share of the colonies that took up a plasmid is this?
- What do the colonies that grew on both plates carry?
Need a reminder? The key ideaShow
The selectable marker finds the transformants. Insertional inactivation finds the recombinants. A foreign gene in the BamHI site of tetR gives colonies that grow on ampicillin and not on tetracycline. In a lacZ vector, white colonies are the recombinants.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. colonies on ampicillin, of them on tetracycline.
Plan. Recombinants lose tetR, so they grow on ampicillin and not on tetracycline.
Step 1. (a) colonies.
Step 2. (b) per cent.
Step 3. (c) They have ampR and tetR whole, so they carry a plasmid that closed without any insert, a non-recombinant.
Answer: colonies; per cent; a plasmid without an insert.
Check. .
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