Incomplete Dominance Examples: Snapdragons, Carnations, and More

📚 Quick Study Guide

• 🧬 Incomplete dominance occurs when the heterozygous genotype results in a phenotype that is intermediate between the two homozygous phenotypes.
• 🌸 Example: Snapdragons. A red-flowered plant (RR) crossed with a white-flowered plant (WW) produces pink-flowered plants (RW).
• 🌷 Another example: Carnations, where similar color blending can occur.
• 🐔 In some chicken breeds, black (BB) crossed with white (bb) can produce gray (Bb) offspring.
• 📝 Unlike complete dominance, neither allele is fully dominant, so the heterozygote expresses a blended trait.
• 🔢 Genotypic and phenotypic ratios in the offspring of two heterozygotes are typically 1:2:1.

🧪 Practice Quiz

1. In snapdragons, if a red-flowered plant (RR) is crossed with a white-flowered plant (WW), what is the phenotype of the offspring?

   1. Red
   2. White
   3. Pink
   4. Red and White striped

2. What is the genotypic ratio of the offspring when two pink snapdragons (RW) are crossed?

   1. 1 RR : 2 RW : 1 WW
   2. 3 RR : 1 WW
   3. 1 RR : 1 RW : 2 WW
   4. 2 RR : 2 WW

3. In carnations, if a true-breeding red flower is crossed with a true-breeding white flower and produces all pink offspring, what type of inheritance is this?

   1. Complete Dominance
   2. Incomplete Dominance
   3. Codominance
   4. Sex-linked Inheritance

4. If a gray chicken (BW) is crossed with a white chicken (WW), what percentage of the offspring will be white?

   1. 0%
   2. 25%
   3. 50%
   4. 75%

5. Which of the following is NOT an example of incomplete dominance?

   1. Snapdragon flower color
   2. Human blood type (ABO)
   3. Carnation flower color
   4. Chicken feather color

6. What is the expected phenotypic ratio in the offspring of a cross between a pink snapdragon and a white snapdragon?

   1. 3 Pink : 1 White
   2. 1 Pink : 1 White
   3. 2 Pink : 2 White
   4. All Pink

7. In incomplete dominance, the heterozygous phenotype is:

   1. Identical to one of the homozygous phenotypes
   2. A blend of both homozygous phenotypes
   3. Expresses both homozygous phenotypes equally
   4. Completely different from both homozygous phenotypes