Chapter 11.5 - Beyond Mendelian Genetics

Incomplete Dominance

Other Examples of Incomplete Dominance

Sickle cell disease in humanss.

AA x aa = Aa (sickle cell trait), where some blood cells will have abnormal shapes


Coloration in some rodents

BB (black) x White (bb) = Gray (Bb)



Blood Types - Multiple Alleles and Codominance

When doing blood type crosses, you will need to know whether at type A or B person is heterozygous or homozygous. Type O's are automatically OO and type AB is automatically AB. Crosses are performed the same as any other.

Multiple Allele Traits

For example: In these aliens, horns are controlled by three allelles

One center horn (A) is codominant with two horns (B). If an alien inherits both alleles (AB), then the alien has 3 horns. A recessive allele (O) results in an alien have no horns. Match the genotype to each of the pictures below.

alien 1alien 2alien 3alien 4

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Polygenic Traits

Environment and Phenotype