• Polygenic (“many genes”) traits– controlled by more 2 or more genes. This is the

case for most traits!– produce a wide range of phenotypes. • Ex: Skin color• Evidence indicates that skin color in humans is

controlled by 3 genes – each of which have a dominant allele and a recessive allele. We represent the 3 genes as A, B and C, take a look at the example:

• this example shows 2 individuals who are heterozygous for all 3 genes and have an intermediate skin color are crossed.

• A Punnett square for this cross would produce 64 possibilities for the offspring.

• What statements can be made about this graph?

Gene interaction map