• Mendel’s experiments only looked at traits in which only one
of the alleles is expressed
COMPLETE DOMINANCE
F1 x F1
Second
Generation
(F2)
Homozygous dominant = purple
Homozygous recessive = white
Heterozygous = lavender
• Mendel’s experiments only looked at traits in which only one
of the alleles is expressed
COMPLETE DOMINANCE
Incomplete dominance: a situation where neither allele dominates
the other and both exercise an influence
on the individual; results in partial
expression of both traits.
F1 x F1
Second
Generation
(F2)
Homozygous dominant = purple
Homozygous recessive = white
Heterozygous = purple and white speckled
• Mendel’s experiments only looked at traits in which only one
of the alleles is expressed
COMPLETE DOMINANCE
Incomplete dominance: a situation where neither allele dominates
the other and both exercise an influence
on the individual; results in partial
expression of both traits.
Codominance:
A situation where both alleles are expressed
fully to produce offspring with a third
phenotype
White (recessive)
Roan
Red (dominant)
Multiple Alleles- ABO Blood
Types
There are 4 major blood groups determined by the presence or absence
of two antigens (A and B) on the surface of red blood cells:
Blood Group
Antigen
A
Has only A antigen on red cells (and B
antibody in the plasma)
B
Has only B antigen on red cells (and A
antibody in the plasma)
AB
Has both A and B antigens on red cells
(but neither A nor B antibody in the
plasma)
O
Has neither A nor B antigens on red cells
(but both A and B antibody are in the
plasma)