Question

a botanist has acquired a group of sweet pea plants. all of the plants have yellow pea pods (the recessive trait), except for one, which has green pea pods (the dominant trait). pea pod color is a trait caused by a single gene. in this tutorial, you will determine how the botanist can identify the genotype of the green pea pod, and how this relates to mendel’s laws and meiosis.
(image: green pea pod (dominant trait), yellow pea pod (recessive trait))
part a - identifying the genotype
how could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?
view available hint(s)
options:

• self - pollinate the green - pod plant.
• cross the green - pod plant with another green - pod plant.
• cross the green - pod plant with a yellow - pod plant.

Explanation:

To determine if a dominant - trait (green pod) plant is homozygous or heterozygous, a test cross is used. A test cross involves crossing the individual with an unknown genotype (the green - pod plant) with an individual that is homozygous recessive for the trait (yellow - pod plant, as yellow pod is recessive).

• If the green - pod plant is homozygous dominant (e.g., GG), all the offspring from the cross with a yellow - pod plant (gg) will have the genotype Gg and show the green - pod trait.
• If the green - pod plant is heterozygous (e.g., Gg), then when crossed with a yellow - pod plant (gg), about half of the offspring will have the genotype Gg (green pod) and half will have gg (yellow pod).

Self - pollinating the green - pod plant or crossing it with another green - pod plant (which could also be homozygous or heterozygous) does not effectively reveal the genotype of the original green - pod plant as clearly as a test cross with a recessive - trait plant.

Answer:

Cross the green - pod plant with a yellow - pod plant.