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Corn Genetics &
Chi- Square Goodness of Fit Test
Pedigrees and probability analysis to follow.
Outline
Highlight some key points in syllabus
Corn color and collection of data (phenotypes)
Chi-Square Analysis
Corn genetics Lab
Application of Chi-Square Analysis
The color pattern in corn is due to multiple genes
Are variations in number of observed phenotypes due to chance alone?
Objective
Complete corn worksheet
Set up Punnett Squares using the genotypes given
Compare expected data to observed data
Perform Chi Square Analysis
Variation of colors—Why?
Corn Kernel Color
Color of aleurone masks endosperm color
Only with colorless aleurone can endosperm color be determined
Determined by several genes
Refer to genotypes in lab manual!
Gene interaction can occur:
Epistasis is a form of gene interaction in which one gene masks the phenotypic expression of another.
Today there are: 3 crosses of corn
Multiple alleles are tested for expression in F2 generation
F1 X F1
Note color differences
Cross CCross D (darker color is purple)Cross F (call purple, may look red!)
Cross C
F1 phenotype
F1 X F1 genotypes
Yellow YYC’Rr X YYC’Rr
Cross D
F1 phenotype
F1 X F1 genotypes
Purple yyPpRr X yyPpRr
Cross F
F1 phenotype
F1 X F1 genotypes
Purple yyCcRr X yyCcRr
Chi Square Statistical “Goodness of Fit Test”
Why do we use it?
.To find out determine if probability are due to chance alone.
An example of how to calculate a Chi Square
Application of Chi Square
Genetic information regarding the corn color patterns are provided in your lab manual.
CORN WORKSHEET IS DUE 3/5