Question

Suppose that the leaf color of a certain plant is controlled by one gene locus with two alleles. At this locus the G allele is associated with orange color and is dominant to the g allele, which is associated with green color. 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?

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

Answer 1

Hi dear, hope you are doing well!

Correct answer: Cross the plant to a plant with green leaves.

Explanation- This is so because we have orange leave which means either our plant has GG genotype or Gg genotype.  When we cross it with green:

If our is GG, then GG × gg which will produce all Gg offspring . These offspring will be all orange and this will confirm we had GG genotype in starting

If our is Gg, then Gg × gg which will produce Gg and gg offspring. So half will be orange and half will be green and this will confirm our starting plant was hetrozygous I.e. Gg.

( this is always know if we want to know the genotype of any plant we cross it with homozygous recessive plant)

Do let me know if something unclear.