1. Multiple Alleles

2. Multiple Alleles More than 2 alleles for a gene
Dominance hierarchy (one allele dominates over the other)
Ex. Fruit Fly eye colour
4 alleles: Red, Apricot, Honey, White
To show dominance hierarchy use first letter of the gene name (E=Eye colour) and a superscript to reflect how dominant it is (1 is most dominant)

3. Multiple Alleles
Red Eyes (E1)= Dominant to all (E1E1, E1E2, E1E3,E1E4)
Apricot (E2): Dominant over honey & white
(E2E2, E2E3,E2E4)
Honey (E3): Dominant over white (E3E3, E3E4)
White (E4): E4E4

4. Multiple Alleles Red Eyes crossed with honey eyes
Red Eyes= E1E1 Honey Eyes= E3E3 E1 E3
E1E3
Genotype: E1E3 Phenotype: Red Eyes

5. A more complicated example…
E2E3= Apricot eye colour (apricot is dominant over honey)
E3E4= Honey eye colour (honey is dominant over white) E2 E3
E2E3
E3E3 E4
E2E4
E3E4
Genotype Possibilities: ?
Phenotype Possibilities: ?

6. Co-Dominance When both alleles are expressed Ex. Spotted chicken
Black and white feathers
Other examples: spotted cow, spotted red and white flower

7. Result= Spotted Chicken!
Co-Dominant
There is NO dominant allele
Both alleles are expressed
Ex. Black Chicken (FBFB), White Chicken (FWFW)
Black (FB)
White (FW)
FBFW
Result= Spotted Chicken!

8. Blood Types Four possible blood types: A, B, AB, O
Multiple alleles and co-dominance
“A” allele (IA) codes for galactosamine on blood cell membrane (allows your body to recognize it as its own)
“B” allele (IB) codes for galactose
“O” allele (i) codes for neither
Both IA and IB are dominant over i, but neither is dominant over the other
IAIB: both galactosamine and galactose are expressed
Galactose: monosaccharide
Galactosamine is a derivative of galactose

9. Blood Types A blood type: IAIA, IAi B blood type: IBIB, IBi
O blood type: ii
AB blood type: IAIB
Example IA IB
IAIB
IBIB i
IAi
IBi

10. Another Example
Example IA i IB
IAIB
IBi
IAi ii
Resulting Blood Types?

11. Donating & Receiving Blood
Giving blood:
Type O: universal donor
Type A: can give to A and AB
Type B: can give to B and AB
Type AB: can give to AB
Getting Blood
- Type O: can only get blood from O
Type A: can only get from A or O
Type B: can only get from B or O
Type AB: can receive from anyone

12. Incomplete Dominance
The alleles blend to form a different heterozygous phenotype
i.e., a red and white flower make a pink flower
Red: CRCR White: CWCW CR CW
CRCW: pink
Other examples: wavy hair, grey sheep, white and black cat= orange cat