A CIESE Collaborative Project

Why isn't the dominant trait the most prevalent?

Materials:

  • Notebooks & pencils
  • Printable Student Worksheets

Objectives:
This investigation is designed so that students can answer these questions:

Why is the dominant trait not always the most prevalent?

Procedures:

Have students form groups of 2 or 3 and give them a copy of the questions below and a copy of the list of dominant and recessive traits. Here are some questions to assist in considering why the dominant allele is not always most prevalent:

1. Can the dominant phenotype give the organism a competitive advantage in nature?

2. Give an example of a dominant phenotype which gives an individual a competitive advantage. See http://www.highlands.edu/academics/divisions/socialcultural/psych/johnson/hnd-domrec.htm for a list of dominant and recessive traits..

3. Does the dominant phenotype always give the organism a competitive advantage in nature? Give an example of a dominant phenotype that does not give individual a competitive advantage and explain.

4. Is it possible that the recessive allele could be more beneficial to the organism than the dominant allele? Would the recessive allele become dominant? Would the recessive allele become more prevalent? What environmental factors could cause an allele that is recessive to become highly prevalent?

Optional challenge: Consider the difference between "dominance as the expression of the dominant allele as the phenotype" to "dominance as the competitive advantage of a certain phenotype in nature." Are they different? Why would they be different?; Why would they be the same?; What is the role of natural selection in creating the difference?