Incomplete Dominance and Co-Dominance BIOLOGY 12 Incomplete Dominance and Co-Dominance

Incomplete Dominance a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele results in a combined phenotype (ie. blend)

Incomplete Dominance two alleles are equally dominant, producing a new phenotype the genotypes are written as normal; heterozygous indicates a blend

Incomplete Dominance example: in cross-pollination experiments between red and white snapdragon plants, the resulting offspring are pink the dominant allele that produces the red color is not completely expressed over the recessive allele that produces the white color

Incomplete Dominance Practice in snapdragons, a pink-flowered plant is crossed with a red-flowered plant write the genotypes of each parent create a punnett square for the cross what is the probability of producing a pink-flowered plant?

Co-Dominance the contribution of both alleles are visible in the phenotype equally and fully both alleles are shown in the offspring (ie. spotted)

Co-Dominance example: cattle can be: red (all red hairs) white (all white hairs), or roan (red & white hairs together) the colours are both shown in the offspring the genotype is now written with superscripts

Co-Dominance Practice in some chickens, the gene for feather color is controlled by co-dominance. the allele for black is B and the allele for white is W. the heterozygous phenotype is known as erminette what is the genotype for black chickens? what is the genotype for white chickens? if two erminette chickens were crossed, what are the possible phenotypes?

Practice Together in certain species of fish, blue scales are incompletely dominant over yellow scales. heterozygous fish show a green phenotype. predict the outcome between two heterozygous fish. BB = blue bb = yellow Bb = green

Predict the outcome between two heterozygous fish. B b BB Bb B b Bb bb

Predict the outcome between two heterozygous fish. Genotype: 25% BB 25% bb 50% Bb Phenotype: 25% Blue 25% Yellow 50% Green

Practice Together in some species of frogs, green skin and purple skin are co-dominant. predict the outcomes between two heterozygous frogs.

Predict the outcomes between two heterozygous frogs.

Predict the outcomes between two heterozygous frogs. phenotype 25% green 25% purple 50% spotted