Dr. Liu did a genetic screen for yeast cells that fail to synthesize leucine (ie. leu^-). She first
exposed the yeast cells to X-ray and then she plated the cells on to a plate containing complete
medium. Then she replicated (using replicate plating technique) the colonies from the complete
medium onto two new plates (plate A and B). Indicate medium type in A and B plate and how
will she find the colony that is Leu- by comparing the colonies on A and B plates?
Solution
Replica plating technique identifies the nutritional auxotrophs by growing the microbes on
complete and minimal media. The complete media contain all the nutrients required for growth
and development of microbe uder study. The minimal media contain all but one nutrient for
which the microbe is supposed to be auxotroph. In the given question, Dr grows the colonies on
plate A (containing complete media) and plate B (containing media that lack leucine). The
auxotrophs which fail to synthesize leucine can grow on the plate A having complete media only.
The colonies of these auxotrophs are absent on the plate B with minimal media which does not
supplement the requirement of leucine by the auxotrophs. This is how, she can find out the Leu-
colonies on the plate A..
Dr. Liu did a genetic screen for yeast cells that fail to synthesize .pdf
1. Dr. Liu did a genetic screen for yeast cells that fail to synthesize leucine (ie. leu^-). She first
exposed the yeast cells to X-ray and then she plated the cells on to a plate containing complete
medium. Then she replicated (using replicate plating technique) the colonies from the complete
medium onto two new plates (plate A and B). Indicate medium type in A and B plate and how
will she find the colony that is Leu- by comparing the colonies on A and B plates?
Solution
Replica plating technique identifies the nutritional auxotrophs by growing the microbes on
complete and minimal media. The complete media contain all the nutrients required for growth
and development of microbe uder study. The minimal media contain all but one nutrient for
which the microbe is supposed to be auxotroph. In the given question, Dr grows the colonies on
plate A (containing complete media) and plate B (containing media that lack leucine). The
auxotrophs which fail to synthesize leucine can grow on the plate A having complete media only.
The colonies of these auxotrophs are absent on the plate B with minimal media which does not
supplement the requirement of leucine by the auxotrophs. This is how, she can find out the Leu-
colonies on the plate A.
