Download Mini-Lesson: Punnett Squares

Intel® Teach Program
Designing Effective Projects
Mini-Lesson: Punnett Squares
Each parent of an organism contributes a gene with two alleles that may be dominant or
recessive. A dominant trait will always be expressed over a recessive trait. This can be
illustrated with a simple chart called a Punnett Square:
Pea Plant Examples
Plant 1 = Dominant Tall (TT) = Tall Plant
Plant 2 = Mixed Hybrid (Tt) = Tall Plant
T
T
T
TT
TT
t
Tt
Tt
Each square represents a potential offspring. Discuss the results and ask students to
explain why each offspring in this example will be tall. Ask students to hypothesize how a
short plant could be produced. Can two tall plants produce a short plant? Complete the
next example:
Plant 1 = Mixed Hybrid (Tt) = Tall Plant
Plant 2 = Mixed Hybrid (Tt) = Tall Plant
T
t
T
t

What percentage of the offspring would you predict to be tall plants?

What percentage will be short plants?

What are the benefits of being able to predict genetic outcomes?
Complete additional examples as needed for student practice.
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