1. Beyond Dominant and Recessive Alleles
11-3, part 2

2. Patterns of Inheritance that are not Simple…
Incomplete Dominance
crosses in which one allele is not completely dominant over the other
a cross between a red snapdragon and white snapdragon yields offspring which are all pink

3. How to do Incomplete Dominance
CR- Red
CW- white
CRCR- Red
CWCW- white
CRCW- pink

4. Cross a red with a white CR CR
CRCW CW CW

5. How to
do incomplete
dominance problems

6. Patterns of Inheritance that are not Simple…
Codominance
crosses in which both alleles contribute to phenotype
roan cattle appear pinkish-brown because the red hair is mixed with the white hair since the alleles for each color are codominant
Human hair sometimes appears to be of different color strands…

7. Patterns of Inheritance that are not Simple…
Multiple Alleles
crosses in which more than two alleles contribute to the phenotype
a rabbit’s coat color is determined by a single gene with four alleles that can produce four different coat colors
human blood types is also controlled by multiple alleles (can be O, A, B, AB)

9. Patterns of Inheritance that are not Simple…
Polygenic Traits
many traits produced by the interaction of several genes
different skin colors and eye colors in humans are controlled by 4-7 different genes