Question

a group of students performed crosses between 10 garden pea plants with purple flowers and 10 garden pea plants homozygous for white flowers. they collected 100 healthy seeds of the f1 generation and grew them. they provided equal amounts of water and sunlight to all the plants. during the flowering season, the students observed that all of the plants had purple flowers.
based on the results of the students experiment, what can the students determine is most likely true about the inheritance of flower color in garden peas?
purple flowers are dominant to white flowers in garden peas.
flower color is determined by a sex - linked gene in garden peas.
flower color is determined by incomplete dominance in garden peas.
white flowers are dominant to purple flowers in garden peas.

Explanation:

When a cross is made between purple - flowered plants and homozygous white - flowered plants, and all the \(F_1\) generation has purple flowers, this is in line with the principle of dominance. In Mendelian genetics, if one trait (purple flowers in this case) masks the expression of another trait (white flowers) in the \(F_1\) generation, the trait that is expressed (purple) is the dominant trait.

• For the option “Flower color is determined by a sex - linked gene in garden peas”: There is no indication in the problem that the cross was sex - specific (e.g., different results for male and female plants), so we can rule out sex - linked inheritance.
• For the option “Flower color is determined by incomplete dominance in garden peas”: In incomplete dominance, the \(F_1\) generation would show an intermediate phenotype (e.g., light purple if purple and white were incompletely dominant). But here all \(F_1\) plants have purple flowers, so incomplete dominance is not the case.
• For the option “White flowers are dominant to purple flowers in garden peas”: Since all \(F_1\) plants have purple flowers, white cannot be the dominant trait.

Answer:

Purple flowers are dominant to white flowers in garden peas.