Part 4: Making your first generation (F₁₎ cross

To make this cross:

1. Be certain, by visual inspection, that your females are virgin. Look for the presence of larvae in the food. You may need to use the stereomicroscope for this.
2. Add 2-3 males of a different strain to your vial of females.
3. Record the parents and date on the vials and in your journal.
4. Check the flies in 2-3 days to see if larvae are present.
5. Remove the parent flies after 4-5 days

Part 5: Examining the F₁Generation

Construct a data table in your journal. The table needs to include:

1) The parents you crossed (P₁)
2) The sex and phenotype of the F₁

Also in your data table, write how long it will take for larvae to become adults. Two days after this you can begin taking data.

Below is one type of data table. Feel free to use it as a template or construct your own. You will need a separate data table for each cross you do. Put this in your journal Remember to add a title to your table!

	Female	Female	Male	Male
	wild-type	purple legs	wild-type	purple legs
Generation
Parental
F₁
F₂

When you have a vial with 30 or more adults, anesthetize them, count the flies by sex and phenotype, and record in your data table.

Part 6: Making the F2 Cross

After your F₁’s have eclosed (adults emerge), wait 2-3 days before making a F₂ cross. Using the procedure from above, obtain 5 virgins from each vial and cross them with 5 males from the same vial. What should your procedure be if you have several different flies with different phenotypes? Complete the cross as before, recording your information in your journal. Examine the F₂ generation as you did with the F₁.

Part 7: Analyzing your crosses

Use your data to construct ratios for the F₁ and F₂ phenotypes.

1. Answer these questions in your journal.

1. Were the parents of your crosses homozygous or heterozygous for their phenotype? The F₁? The F₂? Explain.
2. What are the genotypic and phenotypic ratios of your F₁ and F₂ flies?

2. Create a poster for the rest of the class to see your results. The poster must include pictures or drawings of

1. Male and female P1 flies showing their different phenotypes and genotypes
2. Male and female F1 flies showing their different phenotypes, genotypes, phenotypic ratios and genotypic ratios
3. Male and female F1 flies showing their different phenotypes, genotypes, phenotypic ratios and genotypic ratios

3. Make a drawing of your poster in your journal.

4. Using the F₂ flies, make a prediction on the outcome of an F₃ generation. Explain.

Part 8: Self assessment

At the end of this lesson your journal should contain;

1. A completed table of contents
2. A questions asked in the lesson answered
3. A drawing of your poster
4. Your predictions and explanation of the F₃ offspring.

At the end of this lesson you should be able to:

1. Correctly use and understand new vocabulary words
2. Understand the inheritance pattern of all mutants and while type flies used in class
3. Relate how all sexually reproducing organisms pass traits on to their offspring
4. How variation in a population occurs