In this lesson, students will come to understand that in sexually reproducing organisms, such as humans, typically half of the genes come from each parent.
Without delving into a complicated explanation of the process, the activity in this lesson will help students build an understanding of how offspring inherit genes from their parents. This is prerequisite understanding for further study of genetics at the high school level. This lesson could follow instruction on meiosis or stand on its own.
In this lesson, students will examine a fictional pedigree and determine which gene is responsible for a given trait. The genetic information for individuals is depicted as a jigsaw puzzle. Terms that students will encounter include gene; chromosome; DNA; pedigree; genotype; phenotype; dominant; and recessive.
According to Benchmarks, when asked to explain how physical traits are passed from parents to offspring, elementary-, middle-, and some high-school students express various misconceptions. For example, some students believe that traits are inherited from only one of the parents (e.g., the traits are inherited from the mother, because she gives birth or has most contact as children grow up; or the same-sex parent will be the determiner). Other students believe that certain characteristics are always inherited from the mother and others come from the father. Additionally, some students believe in a "blending of characteristics."
Early middle-school students explain inheritance only in observable features, but upper middle-school and high-school students have some understanding that characteristics are determined by a particular genetic entity that carries information to be translated by the cell. (Benchmarks for Science Literacy, p. 341.)
Note: If you choose to do the second option for the Motivation, the website, Southeastern Michigan Math-Science Learning Coalition, has a list of everything you need to do that activity. You might want to print out and make copies of the student handout, Genetics: You Are Unique, ahead of time.
To set up the lesson, you can adapt the activity described in the "Active Participation" section of Sixth Grade Science: Reproduction and Heredity website. You will have to scroll down to the "Classroom Connectors" section of the page, and look for "Active Participation."
In addition to the questions asked in this activity, you might want to ask these questions:
- How do you think you got the traits that you share in common with your parents, brother, or sister?
- Do you think you got those traits from both parents or just from one of your parents?
- Do you know what genes are? If so, what are they?
A second option would be to do a lesson called Genetics: You are Unique on the Southeastern Michigan Math-Science Learning Coalition website. Note that this lesson requires students to find information from both of their parents, so you should decide ahead of time if this is an appropriate activity for your students.
No matter which motivation activity you choose, have students discuss traits that are inherited. Structure the discussion so that it elicits student ideas, and be sure to determine if students hold any of the misconceptions stated in the Research.
Have students do the activity called Finding a Gene on the Chromosome Map, from the Genetic Science Learning Center website.
Students should read through the first page of this site. When they are done, have them click on the activity, Find the Gene for Whirling Disorder. They should do just the first part of the activity (they should not go on to the bonus questions), and work in pairs to figure out the puzzle. Depending on the level of your students, you may then want to continue with the activity, moving on to the bonus questions. Be sure to read these ahead of time to see if they are appropriate for your students.
Ask students to explain the strategies they used to find the piece of the puzzle responsible for "whirling disorder."
Ask questions such as:
- How far through the generations did you get before starting to understand what gene it was?
- How did you know what gene it was?
- Did both parents possess the "whirling" gene or did just one parent have that gene?
- Which parent passed on that gene to his/her child?
- Did the female child (#3) get all of her genes from her father or does she have a mixture of genes from both parents?
Next, distribute the Gene Puzzle Activity student sheet, and have students color it in to represent the genes for two parents and the genes for their offspring. Students should take two of the 12 listed individuals, name them parents, and then color in new offspring.
The puzzles should demonstrate that students understand that roughly half of the genes come from the mother and half from the father.
Heredity and Genetics, from Science Connection, is a lesson designed to provide students with a general understanding of simple genetics and heredity. It is best for students who have already had some instruction on cells.
From the Access Excellence website, a Take Home Lab called What Are Some Traits in Your Family? is a somewhat more advanced lesson in which students prepare four pedigree designs of their family genetics.