Multiple Alleles

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)

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

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

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: ?

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

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!

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

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

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

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

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