1. Genetics Unit: It’s all about YEAST today! Nov. 29 & 30
Please get the following items:
Get out your journal and yeast pre-lab for a stamp
You will need a writing apparatus
Remember…Genetics VOCAB quiz next week.

2. Warm Up Nov 29 & 30
Why are organisms such as yeast, fruit flies and mice commonly used for genetic research?

3. Warm Up Review
Both yeast and mice reproduce rapidly and with lots of offspring. Therefore you can observe many generations in a short period of time.

4. Learning Targets
I can predict the color of offspring when I cross two yeast parents.
I can use a Punnett Square to predict the genotype and phenotype of the offspring.

5. WHAT SHOWS UP? YEAST Lab
How are traits passed from parents to offspring?

6. What Shows Up? Pre Lab/Background Information
1. Yeast are Fungi. Yeast are single celled, eukaryotic microorganisms.
2. Yeast have mating types instead of sexes. Mating types are “a” and “α” (alpha). When opposite mating types come across each other they secrete a pheromone. A deliberate mating is called a CROSS.
3. Yes, by budding (outgrowth of a parent cell)
4. There are many strains of yeast.
Strain 2 = pinkish red colored (both the a2 and alpha2)
Strain 3 = cream colored (both a3 and alpha3)

7. Yeast Lab Hypothesis and Data
Copy two mating grids neatly onto the petri dish templates on your worksheet.
Predict (in the first grid) the colors of the offspring that show up when you mate each set of parents. Tell me why for each square.
Alpha2
(red)
Alpha3
(cream) a2 a3
First set of parents
Second set of parents

8. Modified Procedural Steps for “What Shows Up?”
Neatly label petri dish along bottom edge with lab group number, period and date.
Neatly draw a mating grid on bottom of petri dish (see your data section!).
Label mating grid (α2 and α3 across the top; a2 and a3 down the side).
Wash hands.
Streak parents by taking a TINY bit of each and putting it on the plate along the top or side….PAY ATTENTION TO YOUR LABELING!!! (use a different toothpick for each mating type and strain..…a total of 4 toothpicks; be careful not to touch toothpick end or damage the agar).
Throw away these toothpicks.

9. Modified Procedural Steps for “What Shows Up?”
Carry out the crosses (mate the yeast!!!) (use a new toothpick for each mating type and strain…a total of 8 toothpicks; be careful not to touch toothpick end or damage the agar)
Throw away all toothpicks; wash your hands.
Predict results for all crosses; record your predictions, using color, on the first grid in your lab notebook. (the second grid will be your actual results).
Incubate at 30°C until next class… upside-down!!
Do Stop and Think q’s on next slide.

10. Stop and Think Questions
Answer the Stop and Think questions in your packet. You may wish to use the textbook for question #3 (see the hint in your packet).
We will collect our Yeast Lab data next class after the yeast has had time to reproduce.
You will have approximately 10 minutes to complete these questions.

11. Notes: Punnett Squares
Knowing genotypes of parents, we can predict the probability of offspring having dominant/recessive traits R RR r Rr
Results:
Genotypes:
50% RR; 50% Rr
Phenotypes:
100% round
Ex: Peas
Round seeds = R
Wrinkled seeds = r

12. Punnett Squares Now you try:
Cross a purple (P) flower plant with a white (p) flower plant. Purple is the dominant color.
P=purple (dominant)
p=white (recessive)
Parent # 1
Parent # 2

14. Good Results (from last year!)