Date: January 26, 2001

Grade Level: 9, 10

Subject(s):

• Science/Genetics

Duration: 50 minutes

Description: This lesson introduces students to genetics. Students learn about Mendel's work, genetic terms (homozygous, heterozygous, phenotype, genotype), the construction of Punnett Squares, and the construction of Pedigree Tests.

Goals: SWBAT (Students will be able to) determine and predict the genotypes and phenotypes of parents and their offspring.

Objectives:

1. SWBAT determine and predict the genotypes and phenotypes of parents and their offspring.
2. SWBAT list and discuss the parts of Mendel’s Law of Segregation.
3. SWBAT define homozygous, heterozygous, phenotype, and genotype.
4. SWBAT use a Punnett Square.
5. SWBAT perform a Pedigree Test.

• text: Biology , 3rd edition by Neil A. Campbell, 1993
• overhead projector
• transparencies (lesson outline)
• Genetics Handouts

Transparencies and Handouts in .pdf format; requires free Adobe Acrobat Reader.

Click the icon to obtain the free Reader.

Vocabulary:

1. Homozygous - Pair of identical alleles for a character.
2. Heterozygous - Having 2 different alleles for a character.
3. Phenotype - An organism's outward appearance.
4. Genotype - An organism’s genetic makeup.
5. Punnett Square - A square used to show all the possible combinations of gametes.
6. Pedigree Test - A test in which you look at the offspring of parents to determine the genotypes of the parents.

Divide students into small groups. Inform them that they will have an opportunity to create Pedigree charts. Pass out the worksheet called "Pedigree Activity," which involves eye color. From the information provided (4 children: 2 brown-eyed and 2 blue-eyed), students will predict the genotypes of the parents and grandparents and construct a Pedigree chart showing the traits for the grandparents, parents, and children. [ Author's Note: Since the ratio of brown to blue is 1:1, students can predict that one parent is homozygous recessive and the other is heterozygous. It doesn't matter which parent is which. The Pedigree chart for the parents and children would look like Pedigree chart D.]

As an extension to the eye color activity, have students choose one offspring. Ask students to predict the children that offspring would have if the offspring mated with a homozygous dominant, a homozygous recessive, or a heterozygous mate (remind students that brown-eyed is dominant). Students should compare the different outcomes in each instance. 

As an alternative to eye color, students can construct Pedigree charts for other traits such as earlobes (free earlobes dominant and attached earlobes recessive) or tongue rolling (rolling dominant and non-rolling recessive).

If there is time remaining at the end of class, conduct a "Quickfire Review." Concepts that can be reviewed include the following:

1. List and discuss the parts of Mendel’s Law of Segregation.
2. Define homozygous, heterozygous, phenotype, and genotype.
3. List other traits that students feel are inherited. Of the traits listed, what do students feel are the dominant and recessive traits of each?

Useful Internet Resources:
* The Biology Project ~ Mendelian Genetics
http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.html

* Pea Experiment
http://www.sonic.net/~nbs/projects/anthro201/exper/

Special Comments: Technology Integration Scenarios:
If a computer and LCD panel are available, connect to the "Biology Project ~ Mendelian Genetics" web site. Complete the monohybrid cross test set with the students as a review of the lesson.