Download Beyond Dominant and Recessive alleles

Beyond Dominant and Recessive
alleles
Against Mendel’s principle…..
 Some alleles are neither dominant nor
recessive.
 Many traits are controlled by multiple alleles
or multiple genes.
Incomplete Dominance
 Incomplete dominance: neither allele is
dominant
 See p. 319
 A red (RR) and white (WW) flower were
crossed and produced pink.
 The pink flower had a genotype of RW
Red+ White= Pink
+
=
Codominance
 Codominance: Both alleles contribute to the phenotype of the
organism.
 Ex. In cattle, red hair allele and white hair alleles are
codominant. They look pinkish, brown, but up close they have
white hairs and red hairs.
 Heterozygous chickens appear speckled, but up close they
have black and white feathers.
Roan Horse
Speckled Andalusian Chickens