Episode FourObservable Traits
Lesson Goal Gather data on an observable trait of you and your classmates; develop hypotheses (testable ideas) about what data you will see/hear.
- Class Survey Worksheet
- A partner or partners
- Hand wipes
- PTC Paper
- A mint/hard candy
Step One – Brush up on Basic Genetics
- Review the following basics of genetics
- Animals typically have two parts of every gene (sometimes things go wrong).
- Each part is called an allele.
- You get one allele from your biological mother, and one from your biological father.
- Your genotype is the “type-o-gene” that you have (made up of alleles).
- Your phenotype is what we see – the physical presentation and appearance (even if we have to look really, really closely to see it).
- Sometimes an allele is dominant. Sometimes an allele is recessive.
- If a dominant allele is paired with a recessive allele, generally the dominant gene is expressed
- Generally, the only way to see a recessive trait is if both alleles are recessive alleles.
Step Two – Develop your Hypothesis
- Define the Problem: The ability to taste PTC is a dominant trait. Will that dominant trait be observed more frequently than the recessive trait (inability to taste PTC)?
- Answer the Question: Is the ability to taste PTC more common than not being able to taste it?
- Choose your Hypothesis: (our testable idea)
- There will be more students who can taste PTC, than students who cannot.
- There will be more students who cannot taste PTC, than students who can.
Step Three – Run your Experiment
- Clean your hands with the hand wipe provided by your teacher.
- Place the entire strip of PTC-saturated paper in your mouth. Wait 5-10 seconds… then carefully spit the paper into the tissue provided for you.
- Use the mint/hard candy if the PTC taste is really horrible. Never taste any substance in a lab unless directed to by your teacher!
- Make a note on Data Table 1 whether or not you tasted the PTC (trust me, you’ll know!)
- Count the number of students in your class who have the dominant trait (can taste PTC).
- Count the number of students in your class who cannot taste the PTC (recessive trait).
- Did anyone have an EXTREME reaction? These folks are the supertasters.
- Add these results to Data Table 1
- Complete the ratio and proportion section of your worksheet
- Complete the graphing section of your worksheet
- Think & Write about this:
Do your findings support or refute your hypothesis?
Do you think your findings are accurate? Why/Why not?
If you were going to run this experiment again, what would you do differently, and why?