Question

Outline an experiment you could use to test a hypothesis about yeast reproduction. Include and identify the following 6 key elements of your experiment:

1) the experimental versus control group

2) the dependent variable

3) the independent variable

4) the standardized variables

5) adequate replication/sample size

Answer 1

1. Standardization: establish relation between cell suspension of particular absorbance and number of colony forming units.

2.

3. Make three groups 1. Growth media control (sterile media with no yeast is inoculated to check contamination during the expriment), 2. Negative control media containing fixed number of yeast cells (say 1 mL of yeast suspension with 0.1 absorbance corresponding to 104 cells added in 100 mL media) with cell division inhibitor 3. Test solution (yeast cells fixed number same as poured in negative control i.e. 0.1 absorbance or 104 cells).

4. Incubate the media in appropriate environment. With time check the absorbance of all groups.

5. Absorbance can be converted to number of colony forming unit by standard curve.

6. Absorbance of test group increases with time taking zero of growth media control and absorbance of negative control should not increase.

7. Here dependent variable is absorbance or CFU which increases in response to independent variable i.e. time which is under control of scientist or experimenter.

8. Absorbance has been standardized with number of CFU to show the easily assessable absorbance data in relevant units.

9. Sample size should be that whole number of samples taken out should not decrease the volume of media by 10% that should also be sufficient to be checked in spectrophotometer so planning should be in that way.