Subject
Science, Math

Activity Overview
When a human egg cell is fertilized with a sperm cell there are many possible gene combinations. This results in great variety of human traits, and the probability of any two humans having identical genetic traits is very small.

Objective
By the end of this activity students should understand the concept of probability in regard to gene combinations during fertilization. This activity is a model of the process of independent and random assortment of genes. Students select "genes" from the egg and sperm cells and observe the resulting combinations in the "offspring."

Materials
empty cans or paper sacks
bottle tops

Activity Outline
Have students:
1. Use two sets of empty containers, such as cans or sacks, to hold the "genes" for the egg and sperm cells. One set is for the genes in the sperm cell, the other set for the genes in the egg cell. The number of containers will correlate to the number of traits you want to study.
2. Use bottle tops as models for genes. Mark them as either dominant or recessive for a particular trait. Then put each "gene" into a separate container.
3. Choose, without looking, one "gene" from each parent and record the resulting trait in the "offspring."
4. Keep a table of the results. Draw a sketch of the resulting offspring.
5. Calculate the mathematical probability of any two of these "offspring" having identical traits or gene combinations.

A follow-up idea is to eliminate the "random" factor. Let students do the activity again, this time deliberately selecting the genes they want. Have them compare this "genetic engineering" activity to the random selection activity done previously.

Assessment
After selecting genes for all the traits, have students draw a picture of the offspring.
Students can compare and discuss results. Were any two offspring identical?

Standards and Benchmarks
Standard 4: Understands the principles of heredity and related concepts
4. Knows that hereditary information is contained in genes (located in the chromosome of each cell), each of which carries a single unit of information; an inherited trait of an individual can be determined by either one or many genes, and a single gene can influence more than one trait
5. Knows that the characteristics of an organism can be described in terms of a combination of traits; some traits are inherited and others result from interactions with the environment