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Probability tests and pedigrees.Supplemental InstructionIowa State University
Leader: Matt C.Course: Biol/Gen 313
Instructor: Dr. Myers & Dr. VollbrechtDate: 02/16/2017
Introduction: This worksheet discusses material covered in the fourteenth and fifteenth lectures (02/13/2017 and 02/15/17). Chapter 3 examines these topics.
Concepts
1. Probability tests.2. Pedigrees.
Material
1. Probability tests.
Here’s just a bit more practice with chi-squared tests.
1. In a certain breed of flowering plant, individuals can be either tall (T) or short (t) given optimal growth conditions. A tall plant is crossed with a short plant and the resulting offspring counts are given below.
Tall Short73 57
a. How many degrees of freedom are in the above example?
b. What would you propose are the genotypes of the two parent plants?
c. Perform a chi-squared test. Does it support or reject your hypothesis?
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2. In the same breed of flowering plant, you have two plants with orange flowers that you cross to produce the following offspring.
Red Flowers Orange Flowers Yellow Flowers72 147 81
a. How many degrees of freedom are in the above example?
b. What would you propose are the genotypes of the two parent plants?
c. Perform a chi-squared test. Does it support or reject your hypothesis?
3. Finally, you cross a tall plant with yellow flowers with a short plant with orange flowers. The resulting offspring are given below.
Tall;Orange Flowers
Tall;Yellow Flowers
Short;Orange Flowers
Short;Yellow Flowers
72 75 70 71
a. How many degrees of freedom are in the above example?
b. What would you propose are the genotypes of the two parent plants?
c. Perform a chi-squared test. Does it support or reject your hypothesis?
2. Pedigrees.
In this section, we’ll analyze some pedigrees for autosomal traits.
1. Observe the following pedigree.
a. What is the mode of inheritance for the trait marking affected family members described above? How do you know?
b. You receive word that the second daughter of I-1 and I-2 has passed away. Additionally, you are notified that the second child of II-3 and II-4 was actually adopted and that the last two children of II-7 and II-8 are twins. Modify the above pedigree appropriately.
2. Observe the following pedigree.
a. Describe the mode of inheritance of the affected trait above. How do you know this?
b. Modify the above pedigree to mark individuals who are known obligate carriers.
c. What is atypical about the above pedigree in terms of the outside population? Is there anything else that is atypical about it?
Things to do next Focus your review on things that were difficult from this worksheet. If it was really
challenging, don’t worry; these are meant to be tough and push your understanding of the topics we covered.
Don’t worry too much about chi-squared tests. Understand how it works, but it’ll only be one question on the test most likely. Pedigrees will get more challenging once we introduce sex-linked traits, so look forward to that.
If you have any questions, ask me in session, in class, or by email. I’m more than happy to help.
Next session (Sunday 02/19/17) will be our review for Exam 2. It will run from 5:00 to 7:00 PM in Hoover 2055, our normal lecture hall. There will not be an SI session in Gilman this Sunday.
