Final answer:
In F1 x F1 crosses, each offspring receives one of four genetic combinations with equal probability, resulting in a 9:3:3:1 phenotypic ratio in the F2 generation when considering two traits with dominant and recessive patterns.
Step-by-step explanation:
In every F1 x F1 fertilization event, each offspring has an equal probability of receiving one of the four combinations from each parent. For instance, if we consider traits like seed colour and texture, Mendel's work showed a phenotypic ratio of 9:3:3:1 for the possible combinations in the F2 generation, which includes:
- 9/16 yellow, round seeds
- 3/16 yellow, wrinkled seeds
- 3/16 green, round seeds
- 1/16 green, wrinkled seeds
This occurs because each parent can contribute a dominant (Y for yellow) or a recessive (y for green) allele for seed colour, and similarly for seed texture (R for round and r for wrinkled). The 9:3:3:1 ratio can also be viewed as two 3:1 monohybrid ratios indicating a dominant and recessive pattern for each trait separately. Using the product rule of probability, we can determine the proportions for each phenotypic combination by multiplying the independent probabilities of each trait.