Biology School Worksheet (Page 2 of 6) in pdf

Biology School Worksheet Page 2

New Information:

Incomplete Dominance

In some cases, an intermediate phenotype is shown

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Neither allele is dominant

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In snapdragons, flower color can be red, pink, or white. The heterozygous condition results in pink flowers (or an

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intermediate trait)

A white snapdragon crossed with a red snapdragon produces all pink offspring

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Two pinks crossed together produce 1/4 white, 2/4 pink, and 1/4 red

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When dealing with incomplete dominance and codominance it does not matter what letter you use, as long as the

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heterozygous condition always denotes the intermediate trait.

•_______________ _______________ is a situation in which both alleles are equally strong and both alleles are visible in the hybrid

genotype.

•When an _________________ phenotype occurs and no allele dominates, incomplete dominance results

Complete the Punnet square for a cross between a homozygous red flowered snapdragon (RR) and a homozygous white-flowered

snapdragon (rr). Give the ratio for the phenotype and the genotype?

-red

-white

-pink

Genotypic ratio___________________

Phenotypic ratio __________________

Codominance

Both alleles can be expressed

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For example, red cows crossed with white will generate roan cows.

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Roan refers to cows that have red coats with white blotches.

This phenotype might seem to support the blending theory. (The

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blending theory predicts pink F1 progeny.)

Biology School Worksheet Page 2