Wearing My Genes: Basic Principles of Heredity
Anita Jacobs Horace Mann
8050 S. Chappel
Chicago IL 60617
(312) 535-6640
Objectives:
This lesson is for special education 5-8th grades. Students will be able to:
1. Explain what heredity is.
2. Distinguish the difference between the dominant and recessive genes.
3. Explain the difference between phenotype and genotype.
4. Predict the results of a monohybrid genetic cross using the Punnett
Square.
Materials Needed:
1. Punnett square (drawn on 8 1/2" X 11 sheet of paper)
2. mirrors
3. marshmallows (marshmallow stars have different shapes and colors)
4. construction paper
Strategy:
An explanation of what heredity is, with student questions and responses.
The students, grouped in two's, will be given a drawing of a pair of jeans, on
the pants pocket the students will find their sex chromosomes, either an
XX=female or XY=male. Students will be given an explanation of what the sex
chromosomes are. Students are then given a mirror, taking a look at themselves,
the students explain what they see. The students will see that everyone has
different or similar traits that are passed from their parents.
Activities
1. Using a peek-a-boo writing paper, students will write a description
of what they see.
2. Given a worksheet titled "Designer Genes", students will do the
following activities: An explanation of what a dominant and recessive
gene is given in the directions. (Ref. The Human Body.) For example,
some of the traits discussed on the worksheet are:
a. Examine the eye color (dark is dominant; blue is recessive)
b. Look for dimples (presence of dimple is dominant; absence is
recessive).
c. Look for attached or unattached earlobes (unattached is dominant;
attached is recessive).
d. Ability to roll tongue into a u-shape (ability is dominant; inability
is recessive).
3. The students will pick one of the above traits and write a possible
genotype for the characteristics they can observe (called phenotype).
For instance, if a person can roll her tongue, she could have either a
RR genotype (the presence of two dominant genes) or Rr (the presence of
one dominant and one recessive gene called hybrid).
4. Students will then use a Punnett square to write their findings.
Draw a square making 4 boxes. Working in pairs, one student will put
his genotype at the top of the box. The other student will put her
genotype on the side of the box. The letters at the top and left of
the square represent the genotypes.
D D
_________________
| | |
D | | |
| | |
|________|________|
| | |
| | |
d | | |
|________|________|
a. After the crossing of each genotype from the female on the side of
the square and the male on the top, the students will then have
their possible genotypes and phenotypes of the offspring.
D D
_________________
| | |
D | DD | DD |
| | |
|________|________|
| | |
d | Dd | Dd |
| | |
|________|________|
5. As a manipulative, use marshmallows of varied sizes and colors to
represent the genotypes of the parents and the possible genotypes of
the offspring.
a. Students will use the same characteristic as in step #3. Have
students choose marshmallows which will represent the dominant and
recessive genes.
b. Using the 4 boxes, the students will place their marshmallows in the
appropriate boxes according to the genotypes.
6. Next, give students a copy of a karyotype. A karyotype is a picture
of the 23 pairs of human chromosomes. In order to prepare, you should
first label each chromosome pair, one with a letter (a for example)
and the other half of the pair with a number (1 for example).
Students will cut the x's and will match appropriate pairs of
chromosomes, starting with 1a, 2b, etc, and then paste or tape the
pairs on construction paper.
Performance Assessment:
Given a puzzle vocabulary the students will try to put together the meaning of
the vocabulary words:
1. heredity 6. recessive gene
2. gene 7. offspring
3. genotype 8. Punnett Square
4. phenotype 9. hybrid
5. dominant gene
Students will construct a Punnett square, and will explain how we inherit
traits.
Conclusion:
From these activities the students will learn:
what dominant and recessive genes are;
how to write a genotype and a phenotype;
distinguish between the genotype and the phenotype.
The students will have a better understanding of what heredity is.
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