Complex Patterns of Inheritance

By: Emily Hess

Multiple Alleles

Multiple Alleles

Definition: Traits are controlled by more that two Alleles.

How will the trait appear?: There are more than two ways the traits can be expressed.


Human Blood type is an excellent example of multiple alleles.

There are 6 different genotypes, and 4 different phenotypes.

Allele Codes for

  • IA Type "A" blood
  • IB Type "B" blood
  • i Type "O" blood


Genotypes Resulting Phenotypes

  • IAIA Type A
  • IAi Type A
  • IBIB Type B
  • IBi Type B
  • IAIB Type AB
  • ii Type O


As you can see, the lower case i is recessive, and A and B are co-dominate.