Pedigrees: Tracing Traits through Generations
Purpose: The purpose of this lesson is to help students apply their understandings
of genetics, inheritance of dominant and recessive traits, and Punnett squares to
Pedigrees. Students will be introduced to Pedigrees. In addition, students will
analyze and interpret Pedigrees.
Objectives:
The Student Will Be Able To:
~Explain how pedigrees are used to study human traits.
~Determine whether a pedigree illustrates a dominant or recessive trait.
~Analyze a pedigree and draw conclusions about the individuals depicted in a
pedigree.
Related Standards:
Virginia Standards of Learning:
BIO.6 The student will investigate and understand common mechanisms of
inheritance and protein synthesis. Key concepts will include:
d) Prediction of inheritance of traits based on the Mendelian laws of
heredity.
h) use, limitation, and misuse of genetic information;
National Science Education Standards:
NSES Content Standard A: Science as Inquiry
• Abilities necessary to do scientific inquiry
NSES Content Standard C: Life Science
• Molecular basis of heredity
NSES Content Standard F: Science in Personal and Social Perspectives
• Personal and community health
Materials and Resources:
Pedigree Activity Sheet
Class Management and Safety:
This activity discusses genetic disorders. It is important that students refer to
individuals with genetic disorders with respect.
Procedures:
Engage (5 min)
Opening question: Draw the Punnett Square for the cross EeTt x Eett
What is the phenotypic ratio for this cross?
Explore (5 min)
Students will be given a Pedigree.
Students will make 2 conclusions about pedigree and formulate one
question about pedigrees.
Explain (15 min)
Students will take notes on the structure and use of pedigrees.
Elaborate (20 min)
Students will complete Pedigree activity sheet.
Evaluate
Students will be evaluated based on the completion of their Pedigree
activity sheet, as follows:
Criteria: Student can determine genotypes of individuals represented in a
pedigree; student can answer questions based on analysis of
pedigree.
Evidence: Student correctly lists genotypes of all individuals on Pedigree;
student correctly answers questions on Pedigree activity sheet.
Scoring:
Question 1: Students will receive one point for each individual
assigned the correct genotype (37 points)
Question 2: Students will receive 4 points for correct answer (4 pt)
Question 3: 1 pt first question, 1 point second question (2 pts)
Question 4 – 6: 2 pts for punnett square, 2 pts for correct answer (4
pts each question, 12 pts total)
Question 7: 2 pts punnett square, 2 pts genotypic ratio, 2 pts
phenotypic ratio (6 pts total)
Question 8: 4 pts correct answer (4 pts)
Total: 65 points
Cleft-Chin Pedigree
Answer Sheet
1. In the chart below, write the genotype for all individuals (1-37) in the Cleft-Chin Pedigree.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
2. Is the Cleft-Chin trait dominant or recessive?
3. What generation (F1, F2, etc.) is individual #8 in?
What generation is individual #36 in?
4. If individual #34 marries a woman that does not have a cleft-chin, what is the probability that
they will have a child that has a cleft-chin? Show your Punnett square.
5. If #27 and #28 have another child, what is the probability that they will have a girl that
doesn’t have a cleft-chin? Show your Punnett square and/or calculations.
6. What will be the expected phenotypic ratio if #29 marries a woman that is heterozygous for
cleft-chin? Show your Punnett square.
7. If #31 marries a man who is heterozygous for cleft-chin, what will be the expected genotypic
and phenotypic ratios for their offspring? Show your Punnett square.
8. What is the expected genotypic ratio for the Parent cross?