Can the genotype for a gray-bodied fly be determined

Virtual Punnett Square Lab

Log on to: http://glencoe.mcgraw-hill.com/sites/dl/free/0078759864/383934/BL_05.html

Objectives:

Construct and analyze Punnett squares for monohybrid genetic crosses given scenarios describing specific Drosophila crosses.

Analyze the expected genotypes and phenotypes that result from each cross.

Procedure:

1. Click the TV/VCR. Then, click the Play button on the video controller. Watch the video about setting up and filling in a Punnett square.

2. On the Biology Lab Navigation Screen, click the notebook on the lab table to perform genetic crosses using Punnett squares.

3. Read the scenario at the top of the screen.

4. Given the scenario, determine the genotypes and phenotypes of the parents involved.

· Select parents to cross by clicking the arrow near Parent 1 and Parent 2. A drop down menu will appear.

· Click the ‘Check Parents’ button.

· If you select the incorrect parents, examine the parents described in the scenario and try again.

· If you select the correct parents, the alleles of the selected parents will appear next to each box of the Punnett square.

5. Given the selected parents, determine the genotypes of the offspring that you expect to result from

the genetic cross.

· Fill in the Punnett square by clicking and dragging the appropriate genotypes at the bottom of the Punnett square to the bottom halves of the appropriate boxes in the Punnett square. If you want to change your selection, you must first drag the genotype that you want to change out of the Punnett square and then drag your new selection to the Punnett square.

· Given the genotypes, determine the phenotypes of the offspring that you expect to result from the genetic cross. Fill in the Punnett square by clicking and dragging the appropriate phenotypes at the bottom of the Punnett square to the top halves of the appropriate boxes in the Punnett square. If you want to change your selection, you must first drag the phenotype that you want to change out of the Punnett square and then drag your new selection to the Punnett square.

· Click the ‘Check Offspring’ button.

· If a genotype or phenotype in the Punnett square is filled in incorrectly, then that part of the box will be highlighted. Examine the parents' alleles to determine the expected offspring and try again.

· If the Punnett square is filled in correctly, record the data in your Table. Use the data to answer the Analysis questions.

6. Record your scenarios and Punnett squares in the spaces below. They will appear on the screen in random order but the answer spaces on this worksheet have been put in sequential order for you.

7. Click the Reset to get a different scenario. Repeat this procedure for all 10 scenarios.

1. Can the genotype for a gray-bodied fly be determined? Why or why not? _Yes, the genotype of a gray-bodied fly can be determined by doing the Punnet square for those types I did. One parent was Gg and the other was gg so the possibilities were GG, Gg, GG, Gg which meant that all the offspring would be gray bodied fly's.______________________

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2. What could you do to determine the genotypes of two gray-bodied flies? Be very specific.

___________________________________________________________________________________

___________________________________________________________________________________

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3. Explain why an organism with a homozygous dominant genotype has the same phenotype as an organism with a heterozygous genotype. __Because the dominant gene always appears in the phenotype, whether or not it is "pure" (homozygous)or "mixed" (heterozygous). The recessive gene does what it says: it is recessive to the dominant gene. So if it comes between the two, the dominant always appears. ________________________________________________

___________________________________________________________________________________

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4. What genetic infomation can be obtained from a Punnett square? What genetic infomation cannot be determined from a Punnett square? ______________________________________________________

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5. It is not necessary to use the word homozygous when describing the genotype of an organism displaying the recessive phenotype. Why is this the case?

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Scenario #1

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #2

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #3

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #4

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #5

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #6

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #7

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #8

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #9

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

Scenario #10

Phenotypes of the parents: ___________________________ X ___________________________

Genotypes of the parents: ___________ X ___________

Phenotype percentages of offspring:

Genotype percentages of offspring:

Which trait is dominant? ____________________________

Which trait is recessive? ____________________________

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