PTC (Mara)

Mara

Principle(s) Illustrated

1. Nervous system

2. Genetics

3. Evolution of taste

Standards

• HS-LS3-3

• Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population

• Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.

• Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Questioning Script

Prior knowledge & experience:

Students will have tasted bitter foods before and may have a basic understanding of Mendelian genetics.

Root question:

Why do some people taste it and some people don't?

Target response:

Ability to taste is based on a protein on your taste buds. Proteins are made based on the genetic code, or DNA of a person. Since each person has different DNA, each person will also have different forms of proteins. Most people will be able to taste PTC because it is a dominant trait.

Common Misconceptions:

Students may think that the papers are different or may not understand the pathway of molecular genetics from DNA to RNA to proteins.

Students may also confuse dominant traits with traits that are the most common in the population. Just because a trait is dominant does not mean that the majority of people will have it.

Photographs and Movies

References

University of Utah Explanation

Carolina Biological PTC Paper

Sample Script

NCBI Article on Genetic Variation Among Populations