Your goal is to find only those plasmids which contain both the gene for ampicillin resistance and the gene for kanamycin resistance. Remember that the ligation left you with many different types of recombinant DNA (see the animation on the Plasmid Ligation page). The transformation you performed (putting your DNA into bacteria) will actually provide you with a way of selecting the plasmids you're interested in.

You will be plating your transformed cells on plates containing ampicillin and kanamycin. You know that any colony which grows on a plate with both antibiotics must contain both genes for antibiotic resistance, and must therefore contain a recombinant plasmid. These colonies are the ones we are looking for. Remember that a colony on a plate is a group of millions of cells which are clones of one another, and arose from a single cell which landed on the plate in that spot.

The image below is an agar plate, viewed from the top. This is an "LB+AMP+KAN" plate, meaning it contains Luria broth (basic nutritional media for bacteria), ampicillin, and kanamycin. The white circles on the plate represent colonies. Click on a colony to peek inside the cells and see what type of plasmids are found there. There are a couple of different types of plasmids in these colonies, so click on several to check them. A new window will pop up; in some browsers, this window may be behind your current window. Click the "Reload" or "Refresh" button in the new window to watch the animation again.