Table 3.

A recipe for the haploid-selection “magic medium.”

Ingredient	Quantity
Dextrose	20 g
Difco yeast nitrogen base without amino acids and ammonium sulfate	1.7 g
SC-Leu-His-Arg drop out mix	2 g
Sodium (or potassium) glutamate	1 (or 1.2) g
G418	0.2 g
L-Canavanine	60 mg
dH2O	to 500 ml

Note: This recipe makes 500 ml of 2 x magic medium liquid, which is subsequently filter-sterilized and mixed with an equal volume of 4% agar to make enough medium for ten 150 x 25 mm Petri dishes with 100 ml per plate. G418 is purchased from GIBCO (Cat # 11811-031) and L-canavanine from Sigma (Cat # C1625). An SC drop out mix contains 6 grams of each amino acid except for L-leucine (12 g). It also contains uracil (6 g) and adenine hemisulfate (1.5 g). Any combination of these components can be “dropped out”; thus SC-Leu-His-Arg refers to SC drop out mix that lacks L-leucine, L-histidine, and L-arginine. To make this drop out mix, each component is weighed, with clumps broken up with a mortar and pestle, and transferred into a large bottle. This bottle is shaken vigorously after each component is added. One can also buy from a “Hopkins mix” QBiogene, which is prepared according to this formula.