Module 6 Mendelian Genetics

Lesson 2 Lab: Mouse Genetics (One Trait)

Many traits have two clear phenotypes, like tall or short pea plants. Sometimes these traits are controlled by a single gene with two different alleles. One is dominant, and the other recessive. When an organism has two copies of the dominant allele, or one dominant allele and one recessive allele, the dominant trait is expressed (tall plants). Only when the organism has two copies of the recessive allele does the recessive phenotype come through (short plants).

In this simulation you will explore mouse coat colour as a single gene trait. You will conduct various breeding cycles until you understand how dominant and recessive alleles work, and until you understand how to determine a mouse’s genotype from test crosses and from observation of phenotype.

Problem (Purpose)

Manipulate the P1 breeding pair and observe the resulting offspring to determine how dominance and recessive alleles create a recognizable inheritance pattern. How can understanding this pattern allow you to predict the outcome of various new crosses? How can the results from a cross determine the genotype of the parents?

Materials

For this simulation you will require access to the Internet and a word processing program to record your results.

Procedure

Open up the following link to the Mouse Genetics (One Trait) Gizmo.

 Put your username and password into the top login box. Locate the “Exploration Guide” by clicking on the lesson info button in the top right hand corner. 

In this investigation, you will follow the instructions listed in the exploration guide for the parts titled:

• Observing Patterns of Inheritance.
• Predicting Genetics Crosses

As you read and follow the instructions, make sure you are able to answer the questions listed for yourself. Some of them will be repeated later in this lab for you to submit to your instructor.

Observation
The top two spots in the Mouse house are the P1, or parental generation. Whichever two mice you place here will breed to create the other five spots you see in the mouse house (the F1 generation). You can place either two black or two white mice as parents to start. What kind of offspring result? Does it matter how many times you click “breed”? The next pair of parents should consist of one white and one black mouse. What offspring result now? Now keep two F1 mice by dragging them into the cages at the bottom. Then clear the house with the “clear” button and drag the two from the cages up into the top breeding spot. Click “breed” to generate the next group of offspring (the F2 generation). What kind of offspring may result from this cross? Breed this group until you get a few mice of both colours in the offspring, or F2.

Module 6: Lesson 1 Assignment

Retrieve your copy of Module 6: Lesson 2 Assignment that you saved to your computer earlier in this lesson. Complete the assignment. 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.