Incomplete Dominance and Codominance - Unsolved Practice Set
Chapter: Principles of Inheritance and Variation | Topic: Incomplete Dominance and Codominance
INCOMPLETE DOMINANCE AND CODOMINANCE - UNSOLVED PRACTICE SET
Topic: Incomplete Dominance and Codominance
Multiple Choice Questions
Q1. Incomplete dominance results in an F1 phenotype that is:
- Identical to one parent
- A blend/intermediate of both parents' phenotypes
- Identical to both parents simultaneously
- Always recessive
Q2. In Mirabilis jalapa (four o'clock plant), a cross between red-flowered (RR) and white-flowered (rr) plants produces F1 plants with:
- Red flowers
- White flowers
- Pink flowers
- Spotted flowers
Q3. Codominance differs from incomplete dominance because in codominance:
- The alleles blend to form a new intermediate phenotype
- Both alleles are fully and separately expressed in the phenotype
- One allele completely masks the other
- Neither allele is expressed
Q4. Which of the following is a classic example of codominance?
- Flower colour in Mirabilis jalapa
- ABO blood group system in humans
- Seed shape in pea plants
- Height in pea plants
Q5. If a red-flowered (RR) plant is crossed with a white-flowered (rr) plant showing incomplete dominance, self-pollinating the F1 pink plants gives an F2 phenotypic ratio of:
- 3:1
- 1:2:1
- 9:3:3:1
- 1:1
Short Answer Questions
Q6. Define incomplete dominance, giving one suitable example.
Q7. Define codominance, giving one suitable example.
Q8. How is the phenotypic ratio in incomplete dominance different from that in a typical complete dominance monohybrid cross?
Q9. Why can codominant alleles not be arranged in a simple dominant-recessive relationship?
Long Answer Questions
Q10. Explain incomplete dominance using the example of flower colour inheritance in Mirabilis jalapa, describing the genotypes and phenotypes seen in the F1 and F2 generations.
Q11. Discuss how codominance differs from both complete dominance and incomplete dominance, using appropriate examples to support your explanation.
APPLICATION / ANALYSIS
Q12. A gardener crosses a red-flowered four o'clock plant with a white-flowered one and obtains all pink-flowered offspring in F1. When these pink F1 plants are self-pollinated, predict the phenotypic ratio you would expect in the F2 generation, and explain your reasoning.
Q13. A student is confused about why blood group AB in humans is not simply "a blend" of A and B, the way pink flowers are a blend of red and white. Explain the genetic difference between codominance and incomplete dominance that clarifies this confusion.