Incomplete Dominance, Co-dominance and Multiple Alleles

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What is Incomplete Dominance?

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A genetic situation where one allele does not completely dominate another allele, resulting in a new phenotype that is a blend of the two traits.

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What is Codominance?

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A genetic situation where both alleles in a heterozygous individual are fully expressed, resulting in offspring with a phenotype that shows both traits equally.

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What are Multiple Alleles?

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A situation in genetics where a gene has more than two alleles, leading to a variety of possible phenotypes.

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Example of Incomplete Dominance in flowers?

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When a red flower (RR) and a white flower (WW) are crossed, the offspring may be pink (RW).

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Example of Codominance in flowers?

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When a red flower (RR) and a blue flower (BB) are crossed, the offspring may be speckled (RB), showing both colors.

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What is the phenotypic ratio of a cross between two speckled flowers (RB x RB)?

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1 red (RR), 2 speckled (RB), 1 blue (BB).

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What is the phenotypic ratio of a cross between a red flower (RR) and a speckled flower (RB)?

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2 red (RR), 2 speckled (RB).

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What is the phenotypic ratio of a cross between a red flower (RR) and a blue flower (BB)?

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All offspring will be speckled (RB), resulting in 4 speckled.

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What does it mean when an allele is dominant?

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It means that the trait associated with that allele will be expressed in the phenotype, even if only one copy is present.

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What does it mean when an allele is recessive?

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It means that the trait associated with that allele will only be expressed in the phenotype if two copies are present.