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LESSON TITLE: Mendelian Heredity
SUBJECT AREA: CP Biology
GRADE LEVEL: 9th grade
TIME ALLOCATION: 1 day (42 minute class)
OBJECTIVES: Students will understand that a unit of heredity is called a gene and genes occur in
different forms called alleles. They will know what a homozygous and heterozygous genotype is and
what the phenotype will display based on its genotype. They will understand how to write genotypic
and phenotypic ratios.
STANDARDS: Life Science
BENCHMARK C: Explain the genetic mechanisms and molecular basis of inheritance.
INDICATOR 6: Explain that a unit of hereditary information is called a gene, and genes may occur in
different forms called alleles (e.g., gene for pea plant height has two alleles, tall and short).
GROUPING OF STUDENTS:
1. Individual work
2. Group work
MATERIALS:
Students: Journal, Pencil, Paper, Prepared
bags of allele cards, worksheets for
charting allele frequencies
Teacher: Plastic sealable bags, scissors,
chalk and chalkboard, worksheets for allele
frequencies
PRIOR KNOWLEDGE NEEDED: Students will know
what a chromosome is and where genes are located.
They understand that DNA carries genetic information
and genetic information is passed from one generation
to the next. They know the process of mitosis and
meiosis.
MODIFICATIONS FOR SPECIAL NEEDS:
Students who are having difficulty with the inheritance of
alleles can repeat the activity with other traits. They can
also repeat the activity by changing the parents’
genotypes and predicting the outcomes. Students will
practice Punnet Squares more.
Learning Disabled: An outline for class notes for mini
lecture will be supplied
Students who show advanced learning and are quick to
pick up the concepts can practice using more alleles for
larger crosses, for example a dihybrid cross. Students
can use on-line resources to research genetic
abnormalities. Students can look at Mendel’s research
involving P, F1, F2 generations. Students can use virtual
labs exploring various genetic crosses.
INSTRUCTIONAL MODEL(S)
1. Individual Work
2. Class discussion
3. Mini lecture
4. Cooperative learning-group work
5. Class Discussion
PROCEDURE AND ACTIVITIES
TIME ALLOCATIONS
1. Student engagement: Ask students to think about their physical
features. Why do they look the way they do? Students contribute
their ideas to the class.
1-2 minutes
2. Ask students to write down the different types of features that
they have and where they may have gotten their features from.
Encourage them to think of their parents or grandparents features
and relate them to themselves. Are they the same, different,
maybe a mix between the two?
2 minutes
3. Class shares ideas of specific physical features.
3 minutes
4. Mini lecture
A. Characteristics/traits transferred by way of genes
B. Genes are pieces of DNA that carry genetic information
from one generation to the next.
C. Parent carries 2 copies of an allele (any one of the
alternative forms of a gene that can affect the phenotype of
an organism- ex. hair color, height, eye color, etc) of a gene
for each characteristic and is received by the offspring
during reproduction. Individuals receive one allele from each
parent.
D. Allele represented by an uppercase letter and a lowercase
letter. Lowercase letter is recessive and uppercase letter is
dominant– give example (earlobe attachment).
E. Explain what homozygous and heterozygous mean and
relate it to recessiveness or dominance.
F. Explain difference between genotype (the set of alleles an
individual has) and phenotype (the physical appearance of
the expressed alleles).
G. Provide examples and have students identify the genotype
and phenotype.
H. Introduce Mendel’s experiments on peas and his findings
about genotypic and phenotypic ratios.
5. Activity involving inheritance of traits using a monohybrid cross
of two heterozygous parents for earlobe attachment.
A. Each student receives a bag with 50 E’s and 50 e’s in it.
B. Students partnered and randomly without looking pull a
letter from their bag, modeling the cross between these two
parents.
C. Students tally mark each cross on a piece of paper, return
the letters to a discard pile and repeat 49 more times.
15 minutes
15 minutes
D. After completion of cross students will determine the
genotypic ratios and phenotypic ratios among offspring and
record this on their worksheet given to them. *see attached
worksheet (Should be 1:2:1 genotypic ratio and 3:1
phenotypic ratio)
6. After all students complete activity each group will contribute
their results to the class by writing their totals for each genotype
possibility on the chalkboard.
7. Students will record the class data on their worksheet and
calculate the genotypic and phenotypic ratios and record them on
their worksheet. (Should be 1:2:1 genotypic ratio and 3:1
phenotypic ratio) Are these ratios consistent with what Mendel
found?
ASSESSMENT
Students will complete handout (in class or at home)
*see attached
Last 5 minutes
(if no time left students can write
their findings on board the
following day)
Name ______________________ Date _______________ Partner _________________
Tables for Activity
Table 1. Genotypes of offspring.
EE
Ee
ee
Table 2. Offspring Ratios for Individual Teams
Genotypes:
Total
(count tallies)
Genotypic Ratio
Homozygous dominant (EE)
Heterozygous (Ee)
Homozygous recessive (ee)
_______ : ______ : _______
Phenotypes:
Phenotypic Ratio
Unattached earlobes (EE and Ee)
Attached earlobes (ee)
_______ : _______
Table 3. Offspring Ratios for Entire Class
Genotypes:
Total
(count for class)
Genotypic Ratio
Homozygous dominant (EE)
Heterozygous (Ee)
Homozygous recessive (ee)
Phenotypes:
_______ : _______ : _______
Phenotypic Ratio
Unattached earlobes (EE and Ee)
Attached earlobes (ee)
__________ : __________
Assignment
Name ___________________________
Period
Date ___________
1. What are the genotypes and the phenotypes of the parents?
2. What does each letter in the bags represent?
3. Describe the genotypes of the parents and offspring using the vocabulary
homozygous and heterozygous.
4. Did table 2 reflect a classic monohybrid cross phenotypic ratio of 3:1 ? If not, what
could be the reason why?
5. What trait is being studied in the activity?
BONUS: Construct a Punnet Square showing the parents and their offspring from
the activity in class. (You may have to refer to your book)
References
Ohio Department of Education. (2007). Teaching, Learning, Lessons, and Units.
Retrieved October 20, 2007, from http://ode.state.oh.us/IMS