Inheritance in Maize (Indian Corn) 

Renee Allen                    Louis Wirth Experimental
l466 W. 113th Place            4959 South Blackstone
Chicago, Illinois (60643)      Chicago, Illinois (606l5)
                               (312) 535-1410
 
Objectives:

To calculate the phenotypic ratios for some monohybrid and dihybrid crosses.

To determine the genotypes of parents from the phenotypic ratios of their
offspring.

Materials needed:
 
mutant corn ears
pencil and paper
straight pins  
calculators

Background:

Commercially available corn represent crosses between various parental 
genotypes.  Results of a cross between pure-breeding purple kernel corn and 
pure-breeding yellow kernel corn produces offspring which are all purple 
(demonstrating dominance).  A cross between two of these offspring produce 3/4 
purple and 1/4 yellow kernel corn.  These are the commercially available ears. 

Strategy:

Obtain ears of corn representing offspring of crosses from various mutant and 
wild type plants from a biological supply company.  Divide the class into groups
of two or three.  Give each group an ear of corn.  Place a pin at one end of a 
row of kernels to mark your starting row.  Using a pencil to point to the 
kernels, one partner should indicate the phenotype of each kernel while the 
other partner keeps a tally. 

Each ear of corn is labeled with a code.

Conclusions:   

1. For each ear of corn, calculate and record the ratio of the phenotypes.
   Divide the number of purple by the number of yellow.  Also, divide the number
   of starchy by the number of sweet.

2. From the data, determine the genotypes of the parents in each cross.

3. How do the actual offspring phenotype ratios compare with the expected
   ratios?