Academic journal article The Science Teacher

A Card Game for Teaching Mendel's Laws, Meiosis, and Punnett Squares: Learning from the Fruit Fly

Academic journal article The Science Teacher

A Card Game for Teaching Mendel's Laws, Meiosis, and Punnett Squares: Learning from the Fruit Fly

Article excerpt

The fruit fly (Drosophila melanogaster) is an ideal subject for studying inheritance patterns, Mendel's laws, meiosis, Punnett squares, and other aspects of genetics. Much of what we know about genetics dates to evolutionary biologist Thomas Hunt Morgan's work with mutated fruit flies in the early 1900s (DNA Learning Center 2011). Many genetic laboratories throughout the world still use fruit flies today (Carlson 2004).

Fruit flies are sometimes used in the classroom, but because live stocks can be difficult to maintain, we developed an activity that substitutes fruit fly cards for live fruit flies. This article describes how to make these cards and implement the activity, which aligns with the Next Generation Science Standards (NGSS Lead States 2013; see box, p. 47).

Laboratory investigation: Materials

We created fruit fly cards for students to study the inheritance patterns of three different traits (Figure 1) using six different samples (Figure 2). Three generations were modeled: P1 (the original parents), F1 (offspring from P1), and F2 (offspring from F1 self-cross). We started with public domain images found on Wikipedia of wild type male and female fruit flies (see "On the web"). We modified the images using Microsoft Paint to represent the various mutations taught in class (Figure 3). To make cards measuring 5 cm X 5 cm (2 inch X 2 inch), we printed the images on white cardstock and manually cut them out. (A quicker option is to print them on business card sheets.)

We labeled all cards with sample number and generation (P1, F1, or F2) and sorted the cards by sample but not by generation. We used about 30 flies for each sample (Figures 4 through 6, pp. 42-43). If more realistic fruit fly generation size is desired, multiply the sample sizes by 5 or 10. The finished cards can be laminated for use in future classes.

Students can complete a worksheet (see "On the web") during the activity, recording data, describing observed patterns, and preparing for class discussion. The worksheet provides a formative assessment.

Materials for each group of 2-4 students:

* Set of cards (all samples and generations; see Figure 3 for number of cards)

* Worksheet (see "On the web")

* Sex identification chart (see "On the web")

Laboratory investigation: Procedure

Students devoted four two-hour class periods to this activity. The activity also could be done in eight 50--to 60--minute class sessions or could be modified if less time is available. For instance, Day 1 could be split over two class periods with one day on data collection and the next day on answering questions and class discussion. The following describes what students should know before the activity, the lesson plans of each day, and suggested summative assessment.

Before the activity

Key concepts of mitosis should be taught and assessed first. In class discussion, explore the concept of chromosomes as pieces of information, emphasizing that new daughter cells are identical to the parent cells. This is important because students will later distinguish between asexual and sexual reproduction.

Day 1: Data collection

We ask: "How do fruit flies inherit traits from one generation to another?" To answer this, students must cross fruit flies and see what appears within the offspring. We explain that students will model fruit fly mating with cards. The instructor may also explain the historical significance of fruit fly genetics and Morgan's work.

Before students begin, we explain the different generations: The two individuals from the P1 generation were mated to create the F1 generation. Then a male and female from the F1 generation were crossed to create the F2 generation. The sex identification chart is then explained, along with how to fill in the data tables in the worksheet (note that Punnett squares are not used until Day 3). …

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