“THE AMAZING MAIZE”
wind
Pollen
 Seeds
Yellow
Smooth
Seeds
(Artificial Selection)
Egg
Multiple Variants of Corn Color
Cross for Seed Color
Purple
Yellow
X
P
F1
Ratio?
Percentage?
Which is the
dominant gene?
F2
Ratio?
Percentage?
Cross for Seed Shape
Smooth/ Starchy
Wrinkled/ Sweet
Recessive
Allele =
Dysfunctional
Enzyme
X
P
F1
Ratio?
Percentage?
F2
Ratio?
Percentage?
Which is the
dominant gene?
Introduction: This laboratory investigates a dihybrid cross as shown in the above
photo of an ear of corn. The four different genes and grain types are identified
in the following photo.
There are four grain phenotypes in the above ear of genetic corn:
Purple & Smooth (A), Purple & Shrunken (B), Yellow & Smooth (C) and Yellow & Shrunken (D). These four
grain phenotypes are produced by the following two pairs of heterozygous genes (P & p and S & s) located on
two pairs of homologous chromosomes (each gene on a separate chromosome):
Dominant Genes
Recessive Genes
P = Purple
p = Yellow
S = Smooth
s = Shrunken