Final answer:
All F1 offspring from crossing true-breeding green-seeded and yellow-seeded pea plants are expected to have yellow seeds, with a phenotype ratio of 100 percent yellow seeds.
Step-by-step explanation:
When crossing true-breeding plants with green seeds with true-breeding plants with yellow seeds, where yellow seed color is dominant, all F1 offspring are expected to be yellow. Since green is recessive and the plants are true-breeding, the green-seeded plants would have the genotype 'yy' and the yellow-seeded plants 'YY'. When crossed ('YY' x 'yy'), all F1 offspring would have the genotype 'Yy', expressing the dominant yellow phenotype. Therefore, the expected phenotype ratio would be 100 percent yellow seeds in the F1 generation. Mendel's experiments with large numbers of pea plants confirmed the expected phenotypic ratios align closely with the laws of probability. If the cross is done with significantly fewer plants, the observed ratio may deviate from the expected due to statistical variance and potential environmental factors like extreme wind conditions.