The document explains codominance, using human blood types as an example where type AB blood (ia ib) expresses both A and B antigens. The probabilities of offspring blood types from two AB parents are outlined, indicating 25% A, 25% B, 50% AB, and 0% O. It also covers codominance in plants and animals, illustrating examples like camellia and roan cows.

1. Biology – Let’s Simplify

3. CODOMINANCE

4. CODOMINANCE IN HUMANS
(HUMAN BLOOD) (IA = IB ) i
Blood Type Alleles
• IA = type A Antigen
• IB = type B Antigen
• IA IB = type A & B
Antigen
• IO or i = No Antigen

5. AB

6. ABO BLOOD TYPE
• Q – Complete a cross with a father & mother that both
have type AB blood. What % of their offspring could
receive each blood group?
• AB = IA IB
• IA IB IA IB
IA IB
IA
IB
IA IA IA IB
IA IB IB IB
A = 25%
B = 25%
AB = 50%
O = 0%

7. CODOMINANCE
SICKLE CELLANEMIA
Haemoglobin
A
CTC
changed
to CAC
CAC
transcribed
into GUG
6 – Valine
form
hydrophobic
chain
Sickle
shaped
erythrocyte
Anemia
O2
deficiency
Substitution
of T by A Clotting

9. CODOMINANCE IN PLANTS
RR
Red Camellia
WW
White Camellia
W
W
R R
RW
RW
RW
RW
Gametes
F1- RW
All White
flowers with
Pink spots.
Same
Phenotype &
Genotype

10. CODOMINANCE IN ANIMALS
BB
WW
B B
W
W
BW BW
BW BW
White Cow
Brown Cow
F1-BW
All Roan
Cows
White
cows with
Brown
spots
Gametes