Final answer:
In a monohybrid cross between true-breeding green-seeded plants (gg) and yellow-seeded plants (YY), all F1 offspring will have yellow seeds due to the dominant yellow allele. A Punnett square demonstrates that the F1 generation will be heterozygous (Yg) and thus display the yellow phenotype.
Step-by-step explanation:
A student seeking to understand the F1 generation resulting from a monohybrid cross in pea plants, where one parent has green seed color and the other has yellow seed color, is exploring a fundamental concept in genetics. When considering true-breeding parent plants, the green seed color is recessive, and the yellow seed color is dominant. According to Gregor Mendel's law of dominance, in a monohybrid cross between a purebred green-seeded plant (gg) and a purebred yellow-seeded plant (YY), all the offspring in the F1 generation will have yellow seeds. This is because the F1 generation will have heterozygous genotypes (Yg), where the dominant yellow allele (Y) masks the presence of the recessive green allele (g).
Hence, the F1 generation will be 100 percent yellow-seeded plants. This can be visualized using a Punnett square, where the alleles from one parent are listed across the top and the alleles from the other parent down the side. The resulting F1 genotypes fill in the table, showing that all combinations result in Yg, which expresses yellow seed color.