Mendelian Inheritance
Review (1 page)
Concept 7: Trait Analysis Orange Eyes and White Skin
Practice (2 pages)
Concept 9: Trait Analysis Vertical Eyes and Tooth
Practice (1 page)
Concept 7: Trait Analysis: Orange Eyes and White Skin 4
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Interpreting the Results
F2 Analysis
How are the orange-eyes and white-skin traits inherited? The total number of progeny in the F2 generation is 527. The F2 phenotypic ratio is approximately 9 black eyes, green skin : 3 black eyes, white skin : 3 orange eyes, green skin : 1 orange eyes, white skin. The simplest hypothesis is that there are two genes, and that this is a dihybrid cross with the two genes exhibiting independent assortment. For one of the genes, orange eyes is recessive to normal black eyes. For the other gene, white skin is recessive to normal green skin. A 9:3:3:1 F2 phenotypic ratio signifies the result of crossing two individuals heterozygous for two separate genes that are assorting independently. For each gene, one allele is completely dominant to the other allele.
If we use o for the orange allele and O for the black (normal) allele, w for the white allele, and W for the green allele, we can follow the cross. Let us first study the parental cross of the orange-eyed, white-skinned MendAlien with the black-eyed, green-skinned MendAlien. 
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  Results of the Cross: The F2 Generation
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