The leaf color of a certain plant is controlled by one gene. For that gene, the allele G = orange and g = green. You have a plant with orange leaves but do not know whether that plant’s genotype is GG or Gg. Which of the following would help you determine the plant’s genotype?

Question

a. cross two true-breeding, orange-leaved plants to each other and then cross one of their offspring to the plant with the unknown genotype
b. change the environment in which the plant grows to find the conditions that cause the leaves to produce the orange color
c. cross the plant to a plant with green leaves
d. cross the plant to another plant with orange leaves

Answer 1

a. cross two true-breeding, orange-leaved plants to each other and then cross one of their offspring to the plant with the unknown genotype

By crossing two true-breeding, orange-leaved plants to each other, you can determine if their offspring all have orange leaves, regardless of their genotype. Then by crossing one of those offspring to the plant with the unknown genotype, you can determine the genotype of the plant with orange leaves.