1. Genetics after Mendel Incomplete and Co-dominant inheritance

2. Simple (Complete) Dominance
Mendel’s work taught us that some traits are dominant and others are recessive
There are other ways that traits can be inherited (non-Mendelian inheritance)
Carl Correns (German botanist) discovered Incomplete Dominance while working with 4 o’clock plants

3. Incomplete Dominance
Condition where 1 allele does not completely dominate the other
Creates a new phenotype (blend of both)
Red+White = pink

4. Incomplete Dominance
For these we use 2 different capital letters to denote genotype (no lower case because no more recessive)
Example:
Parent 1: Red (RR)
Parent 2: White (WW)
F1: all offspring would be heterozygous (pink) or RW

5. Incomplete Dominance

6. Incomplete Dominance
Note: intermediate colour doesn’t always have to make sense
Eg. White cat and brown cat mate to produce an orange cat

7. Co-Dominance Condition where both traits exert dominance
Creates a new phenotype where both alleles are expressed at the same time
In livestock the condition is called ‘roan’

9. Co-Dominance
We use a capital ‘C’ to denote co-dominance, then a superscript to show the allele.
For example, in chickens…
Black (CB CB)
White (CW CW)
Checkered (CBCW)

11. Cross a white cow with a red bull
Example:
-Write C (for co-dominance) and a super script (R=Red, W=white)
-Red haired = CRCR
-White haired = CWCW
-Red and White (Roan) =CRCW
Use a Punnett square to predict offspring:
Cross a white cow with a red bull X

12. CR CR
CRCW CW
100% Roan!! CW

13. Flowers can be co-dominant as well…but we don’t call them ‘roan’, just both colours at once
Example:
Purple and white

14. Co-Dominance examples

15. Incomplete and Co-dominance
You can now continue with your genetics problems up to Set 4.
Have fun!