• During the initial discussion of mutations, assess how much students understand about mutations from their comments. Do not correct misunderstandings yet at that point in the lesson.
• During group discussion of the answers on the handout, circulate around the room, answering students’ questions and clarifying any misunderstandings.
• Collect and check the handouts.

Note: This lesson requires prior knowledge of genotypes, phenotypes, and mutations.

Begin the lesson by challenging students to consider the question, “Can a mutation ever have a good effect on a living thing?” Ask students to share their thoughts with a neighbor for a minute, and then ask for a show of hands from those who think mutations are always harmful and those who think they can sometimes be useful. Call on several students with opposing views to share their ideas. Tell students that the class will be reading two articles about mutations in humans and cats.

Before students read the articles, distribute copies of the handouts for each and have them read the questions (S-B-9-3_Black Cat Gene Questions-Student Version.doc and S-B-9-3_Black Cat Gene Questions-Teacher Version.doc, and S-B-9-3_Got Lactase Questions-Student Version.doc and S-B-9-3_Got Lactase Questions-Teacher Version.doc). Assign half of the students to read the “Got Lactase?” article and the other half to read the “Black Cat Gene” article (see Related Resources). If computers with Internet access are available, have students read the articles online. If not, hand out copies of the articles. Note: “Got Lactase?” is at a slightly more advanced reading level than “Black Cat Gene.”

Have students work individually to answer the questions on the handout. Then, have students work in groups of four (two who were assigned each article) to explain their articles and discuss the answers to their handout questions.

Present a mini-lesson on how mutations can affect the genotypes and phenotypes of populations (S-B-9-3_ Effects of Mutations-Teacher Version.doc). Create a concept map, such as the one in the Effects of Mutations resource. Have students take notes during the mini-lesson and copy the concept map into their notes.

Conclude the lesson by taking a new vote on whether a mutation can ever have a good effect on a living thing. Have several students explain how mutations can be beneficial.

Extension:

• For students who may need opportunities for additional learning, assign the “Black Cat Gene” article. Have students engage in active reading by annotating the text with sticky notes or writing in the margins. Have them use the annotations to paraphrase important parts, note any questions they may have, and mark locations of possible answers to the handout questions. Annotating the text encourages students to think about what they read and increase their engagement with the content.
• For students who are performing above and beyond the standards, assign the “Got Lactase?” article and have them answer the additional question, “How did geneticists use evidence of a ‘selective sweep’ to determine how long ago African lactose tolerance genes arose?” (The geneticists studied DNA samples to see how much of the gene sequences next to the lactose tolerance mutations had been inherited along with the mutations. The amount of DNA inherited with the mutations told them how long ago the mutations appeared.)