Module 8 Population Genetics

Module 8: Lesson 1 Assignment—Part 1

Determining Frequencies

Retrieve your copy of Module 8: Lesson 1 Assignment that you saved to your computer earlier in this lesson. Complete Part 1. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Module 8: Lesson 1 Assignment—Part 2

Frequency Calculation

Retrieve your copy of Module 8: Lesson 1 Assignment that you saved to your computer earlier in this lesson. Complete Part 2. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

Lesson 1: Part B

Get Focused

Can allele frequencies in a gene pool change?

The Amish people are the descendants of Swiss founders who immigrated to the United States in the 1800’s in an effort to renounce technological progress. One of the founders of the Amish had Ellis-Van Crevald syndrome, which causes short stature and polydactyly (extra fingers and toes). Although the allele for Ellis-Van Crevald syndrome is very rare in the Swiss gene pool, most Amish mate within their group, thus the frequency of the polydactyly allele has risen substantially in the Amish population today. 

On the other hand, some populations have allele frequencies that have stayed in relative equilibrium over time. For example, the 23 species of crocodilians have experienced great stability in their allele frequencies in the 200 million years of their existence – to the degree that not one of the 23 species has been forced into extinction in that time.

Why is it important for biologists to keep track of allele frequencies?

The definition of micro-evolution is a change in allele frequencies. If there is a relative increase or decrease in an allele, this acts as a red-flag that indicates to population geneticists that the population is experiencing some kind of pressure and is adapting in response. An increase in the frequency of the lighter coat color allele in ground squirrels versus the darker might indicate that only the lighter squirrels can remain camouflaged and survive in the dry yellow grasses that are becoming prevalent with drought conditions. This could be an indicator of the effects of global warming. 

When we say that populations are evolving (allele frequencies are changing) this is not necessarily a bad thing. Populations under pressure have two options. They can either evolve to adapt to the new conditions, or they become extinct. Clearly, evolution is the more favorable choice. 

In this lesson you will see how the Hardy Weinberg Principle is used by biologists as a toolto determine whether or not allele frequencies are changing and therefore, whether a population is evolving.

At the end of this lesson you should be able to answer the following focusing questions:

• What are the five conditions of Hardy Weinberg Equilibrium?
• What happens when conditions of HW Equilibrium are not met?

Module 8: Lesson 1 Assignment

You will complete two assignments for assessment. In Part 1 of this lesson, you dowloaded and started to complete the Module 8: Lesson 1 Assignment. You will receive further instructions on how to complete this assignment later in the lesson.