Question

a purebred plant that has yellow flowers is crossed with a purebred plant that has white flowers. all the offspring have yellow flowers. which conclusion about yellow flowers is supported by these results?
○ yellow flower color is a dominant trait.
○ yellow flower color is a recessive trait.
○ yellow flower color is a heterozygous trait.
○ yellow flower color is a monohybrid trait.

Explanation:

In genetics, when two purebred (homozygous) organisms with different traits are crossed, the trait that appears in all the offspring is the dominant trait. Here, purebred yellow - flowered and purebred white - flowered plants are crossed, and all offspring have yellow flowers. This means the yellow flower trait masks the white flower trait, so yellow flower color is a dominant trait. A recessive trait would not be expressed in the offspring when crossed with a dominant - trait - carrying purebred. A heterozygous trait refers to having two different alleles, but the offspring here are showing a trait that is expressed over the other, so it's not heterozygous in terms of the conclusion. A monohybrid trait refers to a cross involving one trait, but the question is about dominance, not the type of cross.

Answer:

A. Yellow flower color is a dominant trait.