Punnett Squares: Predicting Pea Plant Traits

SubstitutePlans.com
Science · Life and Earth Science 6-8
SP-SCI68-003 · Free to print and use in your classroom · substituteplans.com
Page 2
Punnett Squares: Predicting Pea Plant Traits
Science · Life and Earth Science 6-8 · Grades 7-8 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student).
Technology
None.
Student
independence
Medium. Students follow a worked example, then work alone.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Ruler (optional)
Goal for today: Students will complete monohybrid Punnett squares and use them to predict genotype and
phenotype ratios of offspring.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Keep the answer key on your desk. You do not need to know genetics to run this lesson.
☐ Optional: write on the board: Capital letter = dominant trait. Lowercase letter = recessive trait.
Say this to start
Good morning! Today is a genetics practice. Scientists use a tool called a Punnett square to predict what offspring
might look like. The reading at the top of the worksheet explains the vocabulary and shows one worked example. Read
it carefully, then try the problems on your own. Show your squares in the boxes.
Run of show
Minutes
What you do
What students do
0–5
Take attendance. Hand out the worksheet.
Settle in and take out a pencil.
5–15
Tell students to read the passage. Then walk through the
worked example aloud: the parents’ letters go on the top
and the side, each box combines one letter from each
parent.
Read the passage and follow the example.
15–32
Tell students to complete Part A (questions 1–4). Remind
them to draw the square and write the percentages.
Draw four Punnett squares and record
genotypes and percent tall or purple.
32–42
Tell students to finish questions 5–9.
Answer the multiple-choice, calculation and
true/false questions.
42–48
Tell students to answer questions 10 and 11. Let partners
compare ideas quietly.
Write short explanations about a mystery
parent and a student’s mistake.
48–50
Collect all worksheets.
Hand in the worksheet.
If things go wrong
• If students are confused by the letters, point out that every box gets one letter from the top and one from the
side.

SubstitutePlans.com
Science · Life and Earth Science 6-8
SP-SCI68-003 · Free to print and use in your classroom · substituteplans.com
Page 3
• If students disagree about the order of letters (Tt or tT), tell them either order is fine; capital first is the usual
habit.
• If students ask whether results are guaranteed, tell them no, and that question 11 is about exactly that.
• If students finish early, use the early finisher list.
Early finishers
• Make up your own cross using the letters R and r (round and wrinkled seeds). Complete the square and the
percentages.
• Explain in two sentences what the difference is between a genotype and a phenotype.
Support and challenge
• Support: Have students complete questions 1, 2, 3 and 5, 6 with a partner and copy the worked example into
the margin.
• Challenge: Ask students to figure out what cross of two purple plants could produce some white offspring, and
to prove it with a square.
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:
Anything the teacher should know: