Incomplete and CoDominance Incomplete Dominance In incomplete dominance

Incomplete and Co-Dominance

Incomplete Dominance • In incomplete dominance, neither allele is dominant so there is a blending of ______ traits _____ when two different alleles for the same trait occur together. • Colors blend together heterozygous • (_______ individuals = 3 rd phenotype) red pink white

Incomplete Dominance RR • In Four O’ Clocks, if you cross a red _____ WW (which is always pure) with a white _____ (that is also always pure) , you get a RW (which pink _____ is always hybrid / heterozygous RW RW

Incomplete Dominance RR and blue • In another flower, if red ____ BB flowers are crossed, they produce a ____ RB flower 3 rd purple ____ • What would be the genotype ratio and phenotype ratio if you crossed two purple flowers?

Incomplete Dominance • Cross of two purple flowers RB X ____ RB ____ • What are gamete possibilities? R B • genotype ratio 1 RR : 2 RB : 1 BB RR RB R red purple • phenotype ratio 1 red : 2 purple : 1 blue BB RB B • Can you have a purple blue heterozygous red or no hybrid blue flower? ___

Codominance alleles contribute to the phenotype of • Both _______ the organism by showing up simultaneously (at the same time) in heterozygous individuals. l In cattle and horses, if you cross red (RR) with a pure ____ white (R’R’), you get (RR’) ______ which produces the color roan _____.

Codominance • These cattle or horses actually have both red and white hairs intermixed, or are spotted. phenotype Roan is a third ______. • If you cross a roan with a white… R’ R’ R RR’ roan R’ R’R’ white RR’ roan R’R’ white

Codominance • Andalusian chickens also show this pattern of inheritance. • If you cross a black (BB) chicken • With a white (B’B’) chicken • You get black+white speckled (BB’)chicken

The End

Codominance • The heterozygous condition, both alleles are expressed equally • Sickle Cell Anemia in Humans SS = normal cells S’S’ = sickle cells SS’= some of each

Problem: Codominance • Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. S S’ GENOTYPES: - SS’ (2) S’S’ (2) - ratio 1: 1 S’ S’S’ PHENOTYPES: - carrier (2); sick (2) - ratio 1: 1 S’ S’S’