Final answer:
The probability of an offspring from the trihybrid cross to have a tall, wrinkled, yellow phenotype is 9/64. Hence the correct answer is option C
Step-by-step explanation:
The probability of an offspring from the trihybrid cross of Mendel in peas, Tt Rr Yy x Tt Rr Yy, having a tall, wrinkled, yellow phenotype can be calculated using the product rule. Ignoring seed color and considering only seed texture, we expect three quarters of the offspring to be round and one quarter to be wrinkled. Similarly, isolating only seed color, we expect three quarters of the offspring to be yellow and one quarter to be green. The sorting of alleles for texture and color are independent events, so the proportion of the offspring having a round, wrinkled, and yellow phenotype is (3/4) x (1/4) x (3/4) = 9/64.
Hence the correct answer is option C