Question

thursday february 12th, 2026- ticket out the door
a plant that is purebred for blue flowers is crossed with a plant of the same species that is purebred for yellow flowers. offspring produced from the cross all have yellow flowers. explain this outcome.
a. the yellow and blue traits are codominant.
b. yellow is a dominant trait, and blue is a recessive trait.
c. blue is a dominant trait, and yellow is a recessive trait.
d. the yellow and blue traits demonstrate incomplete dominance.

Explanation:

• Codominance (Option A) would result in offspring showing both blue and yellow traits (e.g., spotted flowers), which does not match the all-yellow offspring.
• In complete dominance, a dominant trait masks a recessive trait. Purebred (homozygous) parents crossing produce heterozygous offspring, which express only the dominant trait. Here, all offspring have yellow flowers, so yellow is dominant and blue is recessive.
• Option C would result in all blue offspring, which contradicts the given outcome.
• Incomplete dominance (Option D) would result in a blended trait (e.g., green flowers), not all-yellow offspring.

Answer:

B. Yellow is a dominant trait, and blue is a recessive trait.