Question

Genetics Yeast Lab

The Awesome Power of Yeast Genetics Pre-lab questions Two weeks ago, you received three unknown yeast strains. One was lys- (it cannot synthesize its own lysine) while the other two were LYS+. Because they were LYS+, they should be sensitive to high levels of aminoadipate (AA) before spontaneous and/or induced mutations occur that may allow some cells to become AA resistant. The two LYS+ strains differ in the rate at which they accumulate mutations. Two weeks ago, you replica plated these strains onto YPD (enriched medium), -lys (lacking lysine), and AA (high aminoadipate) plates. 1. Which strain(s) do you expect will grow on the-lys plate? 2. Which strain(s) do you expect will grow the best on the AA plate? 3. You may discover that one LYS+ strains grows less well than the other on the UV-irradiated side of a YPD plate. What is a plausible genetic mechanism for this result? 4. Propose a mechanism to explain how some cells from the LYS+ strains could grow on the UV-irradiated side of the AA plate. 5. Propose a mechanism to explain how some cells from the LYS+ strains could grow on the NON UV-irradiated side of the AA plate.

Answer 1

Answer 1:

It is given that there are two types of strains, one is LYS- and the other is LYS+.

Cells which are LYS- cannot make the amino acid lysine by themselves, and need lysine supply from outside to grow.

On the other hand, LYS+ cells can make lysine on their own and are not dependent on the external medium for lysine.

Thus, on medium lacking lysine, only the LYS+ strains will grow.

Answer 2:

The LYS+ strains can accumulate mutations which make them resistant to aminoadipate (AA). Thus, in a media which contains AA, LYS+ strains should be able to grow.