Simple, Incomplete, and Codominance Genetics

Punnett Squares are used to show the possibility of inheriting a single trait. Each parent has two alleles for a trait but will only pass on ________ of the alleles.

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In the P generation, a homozygous dominant tall pea plant was crossed with a homozygous recessive short pea plant. Show the cross below and write the genotypes and phenotypes of the F1 generation.

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If you cross 2 heterozygous two pea plants for height, what are the genotypes and phenotypes of the offspring?

• Genotypes: 25% TT, 50% Tt, 25% tt

  Phenotype: 75% Tall, 25% Short

• Genotypes: 50% TT, 25%% Tt, 25% tt

  Phenotype: 75% Tall, 25% Short

• Genotypes: 0% TT, 50% Tt, 50% tt

  Phenotype: 50% Tall, 50% Short

• Genotypes: 100% TT, 0% Tt, 0% tt

  Phenotype: 0% Tall, 100% Short

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Incomplete Dominance Practice Problem Answer: A red snapdragon flower was crossed with a pink snapdragon flower. Complete the cross and determine the genotypes and phenotypes of the offspring. (Refer to the provided diagram for genotypes and phenotypes)

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Codominance Example: A white flower was crossed with a red and white flower. Complete the cross and determine the genotypes and phenotypes of the offspring.

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Incomplete dominance occurs in cats, which allows them to be Black, White, or gray as shown on this Punnett square. The percentage of the offspring that will be white is (a)   .

• 25
• 50
• 0
• 100

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Match the following: Referencing the graphic above, read the rows in the table below which describe crosses between flowers in the incomplete dominance situation described in the graphic.  Match the correct color for each one.

• pink

• Two white-flowered parents reproduce. What color will 100% of the offspring be?

• white

• Two red-flowered parents reproduce. What color will 100% of the offspring be?

• red

• Two pink-flowered parents reproduce. What color will 50% of the offspring be?

In chickens, black is co dominant with white feathers. Which cross would result in 50% black and white feathers?

• BW x BW

• BB x WW

• BW x WW

• WW x BB

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In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for white is W. The heterozygous phenotype is known as erminette (black and white spotted). Match the following genotypes to their phenotypes

• Erminette (Black and white feathers)

• BW

• Black feathers

• WW

• White feathers

• BB

Having a Widow's Peak is dominant (W) over not having one (w). If parent A (WW) and parent B (ww) have a child, what is the likelihood that--

• Ww

• The genotype of these children

• 100%

• The child will have a widow's peak

• 0%

• The child will not have a widow's peak

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NGSS.HS-LS3-1

NGSS.HS-LS3-2