analyze the experiment and answer the questions in the worksheet

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Punnett Square Virtual Lab
Accessed the virtual lab at: http://glencoe.mheducation.com/sites/dl/free/0078757134/383934/BL_05.html
Heredity
How are traits passed from parents to offspring?
A trait is a physical characteristic such as color or size that is inherited by an offspring from its parents. The genes that control a trait come in pairs, one gene from each parent. We represent these gene pairs by writing a combination of two capital or lowercase letters. For example, if one parent contributes a gene for blue eyes (C), and the other parent contributes a gene for brown eyes (c), then we write the offspring's eye color trait as Cc. This combination of the two genes that determine the trait is called a genotype. Each letter in a gene pair stands for one form of the trait. The forms of a trait are called alleles. In this example, the alleles are blue eye color and brown eye color. The two types of alleles are dominant and recessive. A dominant allele is written as a capital letter, and a recessive allele is written as a lowercase letter. If a gene pair contains a dominant allele, then the offspring will show this dominant trait. Recessive alleles can only show up when there is no dominant allele present to suppress them. The physical form of the trait that shows up is called a phenotype.
In this Virtual Lab you will use a Punnett square to find possible gene combinations for fruit flies (Drosophila) a common organism used in the lab to examine genetic crosses and development.
Prelab Questions
Log onto the virtual lab Punnett Squares website and answer these questions.  Click on the Information button on the screen to help answer these questions and understand what you will be doing.
1. What is a trait?
2. What are genes? How are they related to traits?
3. How are gene pairs written out?
4. What is a genotype?
5. What are dominant and recessive alleles? How are they written out?
6. What is a phenotype?
Objectives:
• Use Punnett squares to identify the outcomes (both genotypes and phenotypes) of genetic crosses.
Procedure:
1. Click the TV. Watch the video about Punnett squares. 
2. Click on the notebook on the table. This will set up the Punnett square that you will fill in following the Scenario directions (also use the directions on the left side of your screen).
3. Click on the parent arrows to select each parent, then click on Check Parents to see if you are correct (and show each parent’s alleles).  
4. Click and drag Possible Genotypes into the boxes of the Punnett square. If you want to change your selection, first drag the previous genotype out of the Punnett square.
5. Click and drag Possible Phenotypes into the boxes of the Punnett square. If you want to change your selection, first drag the previous phenotype out of the Punnett square.
6.  After you have filled all four boxes of the Punnett square, click the Check button to check your matches. Incorrectly matched phenotypes will be highlighted in yellow. Correct your matches and click the Check button again.
6. When the Punnett square is correctly filled in, write down your observations in the table below.
7. Repeat the above procedure for three more scenarios. To change scenarios, click on the Reset button.
8.  After recording your data in the table below, answer the following questions.
Table.
Scenario Number Genotype of Parent 1 Genotype of Parent 2 Ratio of Offspring Genotypes Ratio of Offspring Phenotypes

Conclusion Questions.
1. For one of the monohybrid crosses you performed in this Investigation, describe how to use the phenotype ratios to determine the percentage of offspring displaying each trait.
2. What is the difference between a genotype and a phenotype?
3. How are alleles and traits related? Explain using an example.
4. In pea plants, purple flower color (P) is a dominant allele, while white flower color (p) is recessive allele. If a pea plant has the genotype Pp, what is its phenotype?  Explain your answer.
5. Can the genotype for a gray-bodied fly be determined?  Why or why not? Describe all of the possible genotypes for a fly with that phenotype.
6. Explain why an organism with a homozygous dominant genotype has the same phenotype as an organism with a heterozygous genotype.
7. What genetic information can be obtained from a Punnett square?  What genetic information cannot be determined from a Punnett square?