Activity 12.3 (Form 5 Biology Textbook Exercise and Answer)

Activity 12.3:
To study the level of human tongue sensitivity towards phenylthiocarbamide (PTC) solution

PTC taste trait can be classified into specific groups.

Drinking water, PTC paper

1. Rinse your mouth with clean water before starting the activity.

2. Place a piece of PTC paper on your tongue for a few seconds.

3. Record your tongue sensitivity based on the taste of the PTC paper in the results table.

4. Remove the PTC paper from your tongue. Repeat the above steps with other pupils.

5. Build a bar chart based on the results that you obtained.


1. What is the type of variation for PTC taste based on the shape of the graph that is plotted?

2. Is the PTC taste trait dominant or recessive? Explain.

Is the hypothesis accepted? Suggest a suitable conclusion.

1. PTC taste is a discontinuous variation in which there are groups of pupils who can taste PTC and there are groups which cannot taste PTC.

2. PTC taste is a dominant trait. An individual who can taste PTC has either TT or Tt genotype whereas individual who cannot taste PTC has tt genotype.

Hypothesis is accepted. Trait for PTC taste can be classified into specific groups.

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