Question

1. Which transformation(s) would indicate if your yeast strain is auxotrophic for leucine? Explain.

Answer 1

• Minimal media contains nutrients in the minimal amount for survival of bacteria.
• Prototroph and auxotroph are terms referred to strains of bacteria on their ability synthesize nutrients like amino acids, nucleic acids, minerals, vitamins etc.
• Prototrophs are wildtype strains, which can synthesize nutrients required for their cellular functions.
• These bacteria can grow on minimal or basal media without supplementary nutrients.
• Auxotrophs are mutant strains, which have lost the capabilities of synthesizing specific nutrients.
• Auxotroph can grow on minimal media, only when the specific nutrient (as per the auxotroph mutant) is supplemented to the media.

• Thus, to test the process of transformation, the recipient cell: should not be able to synthesize leucine (leu-).
• The DNA to be transformed should have intact Leucine (leu+).
• Before transformation auxotrophic strains will not form colonies on minimal media.
• After transformation, with leu+ gene, prototrops for leucine will form colonies on minimal media.