1. A half shaded circle or square
Track the Trait…
Objective: To demonstrate how to trace a trait through a family tree
Bell work:
Look at the figure to the right
What shape do you think represents a female?
A circle
What about a male?
A square
What do you think represents a carrier of a trait?
A half shaded circle or square
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2. Track the Trait… Heterozygous Hybrid Carrier What You Need to Know:
A pedigree is a way of tracing a trait through a family tree. Rules for reading a pedigree are as follows:
We use specific shapes and shading to signify certain individuals:
Affected female = solid circle
Affected male = solid square
Unaffected female = clear circle
Unaffected male = clear square
Heterozygous Hybrid Carrier
Carrier female = half shaded circle
Carrier male = half shaded square
© Getting Nerdy, LLC

3. Track the Trait… I. II. III.
We use specific numbers to specify the different generations and the birth order of individuals:
Generations (entire lines of individuals) are identified by Roman numerals (I, II, III, IV…).
Siblings are placed in birth order from left to right. All individuals are labeled with numbers (1, 2, 3, 4, 5…). I. 1 2
II. 1 2 3 4 5 6
III. 1 2 3 4 5 6 7
We would name a child II-3 if he/she was in the second generation and was the 3rd child. Is the child in position II-3 in the above picture a boy or girl?
© Getting Nerdy, LLC

4. Now, put your knowledge to the test
Now, put your knowledge to the test. Complete the following pedigrees on your paper and see if you can Track the Trait! I.
II.
III. 1 2 3 4 5 6 7
© Getting Nerdy, LLC