incomplete and codominance worksheet

2025 Vertis

2 min read 10-12-2024

Meta Description: Master incomplete and codominance! This comprehensive guide provides a detailed explanation of both concepts, along with a printable worksheet and answer key to test your understanding of inheritance patterns beyond simple dominance. Perfect for biology students! (158 characters)

Understanding Inheritance Patterns Beyond Simple Dominance

In basic genetics, we learn about simple dominance, where one allele completely masks another. However, not all inheritance follows this simple pattern. Two important exceptions are incomplete dominance and codominance. This article will help you understand these concepts and provide a worksheet to test your knowledge.

What is Incomplete Dominance?

Incomplete dominance occurs when neither allele is completely dominant over the other. The heterozygote displays a blend of the two parental phenotypes. A classic example is flower color in snapdragons. A red-flowered plant (RR) crossed with a white-flowered plant (rr) produces offspring with pink flowers (Rr). The pink flowers represent a blending of red and white.

Key Feature: Heterozygotes show an intermediate phenotype.

What is Codominance?

In codominance, both alleles are fully expressed in the heterozygote. Neither allele masks the other; instead, they both contribute to the phenotype. A prime example is human blood type AB. Individuals with genotype AB express both A and B antigens on their red blood cells.

Key Feature: Both alleles are fully expressed in the heterozygote.

Distinguishing Incomplete Dominance from Codominance

It's crucial to understand the difference:

Feature	Incomplete Dominance	Codominance
Heterozygote	Intermediate phenotype (blending)	Both phenotypes expressed simultaneously
Example	Snapdragon flower color (pink from red & white)	Human ABO blood type (AB)
Allele Interaction	One allele partially masks the other	Neither allele masks the other

Practice Makes Perfect: Incomplete and Codominance Worksheet

Here's a worksheet to help solidify your understanding. Remember to show your work!

(Downloadable Worksheet Here - Link to downloadable PDF of worksheet)

Worksheet Questions (Example):

1. Incomplete Dominance: In a certain breed of chicken, feather color shows incomplete dominance. Black feathers (BB) are dominant to white feathers (bb). What feather color would a heterozygous chicken (Bb) have?

2. Codominance: A cow with red fur (RR) is crossed with a cow with white fur (WW). If fur color exhibits codominance, what would be the phenotype of their offspring (RW)?

3. Problem Solving: A certain type of flower exhibits incomplete dominance for petal color. Red (RR) crossed with white (WW) produces pink (RW). If you cross two pink flowers (RW x RW), what are the genotypic and phenotypic ratios of the offspring? Show your Punnett square.

4. Identifying Inheritance Patterns: You are given a plant with variegated leaves (a mix of green and white). Based on your understanding of incomplete and codominance, explain the possible inheritance pattern at play.

(Answer Key Here - Link to downloadable PDF of answer key)

Conclusion

Understanding incomplete dominance and codominance is key to a comprehensive grasp of genetics. They demonstrate that inheritance patterns are more diverse than simple dominance suggests. By working through this worksheet, you can strengthen your understanding of these important concepts and apply your knowledge to solve genetics problems. Remember to always review your answers and consult additional resources if needed. Good luck!