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:

When purebred (homozygous) plants are crossed, the trait that appears in all offspring is the dominant trait. Here, yellow - flowered purebred plant crossed with white - flowered purebred plant gives all yellow - flowered offspring. So yellow flower color masks the white flower color, which is characteristic of a dominant trait. A recessive trait would not show up in the \(F_1\) generation when crossed with a purebred dominant (if it was recessive, and assuming simple Mendelian inheritance). A heterozygous trait refers to the genotype (\(Aa\)) not the phenotype description. A monohybrid trait is related to a cross involving a single trait (which this is, but that's not the conclusion about the nature of yellow - flower color).

Answer:

Yellow flower color is a dominant trait.