Genetics after Mendel Incomplete and Co-dominant inheritance

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

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

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

Incomplete Dominance

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

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’

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)

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

CR CR CRCW CW 100% Roan!! CW

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

Co-Dominance examples

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