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Submitted by Asher Davison Lexington H.S. Lexington, MA and Trudi Leone, consultant

1. Open GenScope with the dragon species. Create a file with a male, Ricky, who has the wing alleles ww and a female, Lucy who has WW.

2. Note that Ricky, needing wings to soar high above the sultry strains of his Cuban band, indeed has them. Lucy, as effectively an indentured servant, does not.

  1. Do you think that it is possible for their son, Little Ricky to have wings?
  2. Do you think that it is possible for Little Ricky not to have wings?

3. Test your hypothesis by mating Lucy and Ricky in the Pedigree window.

  1. What do the results suggest about Lucy’s genotype for wings?

(If you’re not convinced of your answer, check Lucy’s and Ricky’s genotypes using the Chromosome tool.)

4. Is it possible for the Ricardo dragdens (F1) to produce winged grand-dragdens (F2)? Explain.

5. Test your hypothesis.

What fraction of your grand-dragdens have wings?

Does this match the results predicted by a Punnett square?

Show by making one!

6. Can you tell the genotypes of the unwinged grand-dragdens by asking the Pedigree window to "Show Wings"?

Why or why not?

7. Determine the genotype of an unwinged grand-dragden without using the chromosome tool.

Hint #1: Experiment thoughtfully with further breedings.

Hint #2: The question can be answered easily with one breeding.

8. Perform this test experiment on several of the unwinged grand-dragdens. You may want to use the scissors to clear the screen of prior results  –  after recording them and drawing a conclusion!

How many of the grand-dragdens are homozygous for the W allele? Does this correspond well with the Punnett square you constructed in step 5?

9. Geneticists have a fancy, exciting name for the experimental cross you performed in steps #7 and #8. Since the goal of the test is to unearth the genotypes of the dragons showing the dominant phenotype by making an experimental cross, we call this a TEST CROSS.

Pretty neat, huh? This is not just any cross used to make a test, but one with the particular goal explained above.

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