Multiple Choice
If you look at a blood sample from a person who is heterozygous at the sickle cell locus you will see both normal circular red blood cells and sickle-shaped red blood cells. This is an example of
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13. Mendelian Genetics
Incomplete Dominance vs. Codominance
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Flower color in snapdragons is an example of incomplete dominance. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the progeny plants will be __________.
A
100% pink
B
100% red
C
50% pink and 50% red
D
25% white and 75% red
E
25% red, 50% pink, and 25% white
Verified step by step guidance1
Understand the concept of incomplete dominance: In incomplete dominance, the heterozygous phenotype is a blend of the two homozygous phenotypes. In this case, red (RR) and white (WW) flowers produce pink (RW) flowers.
Identify the genotypes of the parent plants: Since both parent plants are pink, their genotype is RW.
Set up a Punnett square: Place one parent's alleles (R and W) on the top and the other parent's alleles (R and W) on the side of the square.
Fill in the Punnett square: Combine the alleles from each parent to fill in the four squares, resulting in the genotypes: RR, RW, RW, and WW.
Determine the phenotypic ratio: Count the genotypes to find the phenotypic ratio. RR results in red flowers, RW results in pink flowers, and WW results in white flowers. The ratio is 1 red (25%), 2 pink (50%), and 1 white (25%).
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