Assume you had a round seed garden pea plant and you wanted to find out whether the round seed plant was homozygous or heterozygous. What would you do? (Round is dominant to wrinkled seed)
Cross it with a wrinkled seed.
rr=wrinkled.
Rr x rr
Progeny: 1 Rr 1 rr
RR x rr
Progeny will all be Rr and will all be Round
To determine whether the round seed plant is homozygous or heterozygous, you can perform a test cross. Here's how you can go about it:
1. Identify a recessive wrinkled seed plant: In order to perform the test cross, you need a plant with wrinkled seeds. Obtain a pea plant that has wrinkled seeds and is known to be homozygous recessive (rr) for the seed shape trait.
2. Crossbreed the round seed plant with the wrinkled seed plant: Now, you need to crossbreed the round seed plant (the one you want to determine the genotype of) with the wrinkled seed plant. This can be accomplished by transferring pollen from the round seed plant to the stigma of the wrinkled seed plant, either artificially or through natural pollination.
3. Observe the offspring: Allow the cross-pollinated plants to develop and produce seeds. Collect and evaluate the seeds from the resulting offspring.
4. Analyze the ratios: Count the number of offspring with round seeds and wrinkled seeds. If all the offspring display round seeds, it indicates that the round seed plant is homozygous dominant (RR). On the other hand, if you observe a 1:1 ratio of round to wrinkled seeds in the offspring, it suggests that the round seed plant is heterozygous (Rr).
By performing this test cross and observing the phenotypes of the offspring, you can determine whether the round seed plant is homozygous (RR) or heterozygous (Rr) for the seed shape trait.