cell biology course

Question

1. Propose how you would experimentally determine which X, Y, and Z yeast strains correspond with which UCC strains (names and genotypes given at the bottom end) if you had access to the following: 
2. The data on the bottom(table)
3. X, Y, and Z cultures 
4. YPD plates (contain all nutrients yeast need to grow) 
5. -Leu -Trp plates (contain all nutrients except leucine and tryptophan) 
6. 23°C incubator 
7. 37°C incubator 

	Growth at
	23°C	37°C
X	+	-
Y	+	-
Z	+	+

The UCC strains:

name genotype

1. UCC2332 MATalpha Leu- Trp+ CDC13
2. UCC2747 MATalpha Leu+ Trp- cdc13-1
3. UCC2356 MATalpha Leu- Trp+ cdc13-1

some background information if needed;

Part 3: Using yeast genetics for cell identification

Imagine that you have three unlabeled S. cerevisiae yeast strains of different genotypes, how can you identify which is which?

Two strains have a temperature-sensitive mutation (cdc13-1) in the CDC13 gene, which encodes a telomere-binding protein. A cdc13-1 strain grows fine at 23 ̊C but arrests in G2 phase when grown at 37 ̊C. Leu-means that the cell cannot synthesize leucine, whereas Leu+cells CAN make leucine. On an agar plate lacking leucine, a Leu-cell cannot grow, but a Leu+cell will make leucine and will grow. Same goes for tryptophan (Trp).

PLEASE INDICATE STEP WISE EXPERIMENT I WOULD DO! THANK YPOU FOR THE HELP

Answer 1

To answer this question we need to test each strain for its ability to grow on rich medium at 37 degrees and 23 degrees. That will tell us which strain is CDC+.

Then we need to make Leu+ and Trp+ plates, by spreading leucine on three leu-trp-plates, and tryptophan on three other leu-trp-plates.

We can then streak each strain onto 2 YCP plates, and 1 Leu+ and 1 Trp+ plate. The YCP plates (rich medium) go into 23 deg or 37 deg incubators, one for each strain in each incubator.

To test for leu and trp, we streak each strain onto one plate of Leu+ and one of Trp+. These plates are incubated at 23 degrees, because strains 2 and 3 can only grow at low temperature.

In the morning we should be able to match the phenotypes we observe with the genotypes of 1, 2, and 3.

Strain 1 will be 37deg+ on rich medium. No other strain has that phenotype.

Note that the question as posed didn't allow us to distinguish strains 2 and 3 from one another. I had to add in the step to make Trp+ and Leu+ plates in order to determine their genotypes.

Strain 2 will be able to grow on Leu+ but not Trp+ plate.

Strain 3 will be able to grow on Trp+ but not Leu+ plate.

Answer 2

Here's a step-by-step experimental plan to determine which X, Y, and Z yeast strains correspond with which UCC strains:

1. Label three YPD plates as X, Y, and Z, respectively.
2. Using sterile techniques, streak the X, Y, and Z cultures separately onto their respective YPD plates.
3. Incubate the plates at 23°C for 2-3 days until colonies are visible.
4. Using sterile techniques, pick one colony from each YPD plate and streak it onto a Leu-Trp plate.
5. Incubate the plates at 23°C for 2-3 days until colonies are visible.
6. Pick one colony from each Leu-Trp plate and streak it onto a new YPD plate.
7. Incubate the plates at 37°C for 2-3 days until colonies are visible.
8. Observe the growth of the colonies on the YPD plates at 23°C and 37°C.
9. Match the growth patterns with the known genotypes of the UCC strains to determine which X, Y, and Z yeast strains correspond with which UCC strains.

Based on the given genotypes and the experimental results, the X strain corresponds to UCC2332, the Y strain corresponds to UCC2356, and the Z strain corresponds to UCC2747.

Note: The above experiment assumes that each X, Y, and Z culture is a pure culture with only one genotype present. If the cultures are mixed or contaminated with other strains, additional steps such as plating on selective media and/or performing genetic analyses may be necessary to obtain accurate results.