What is the probability that a cross between a true-breeding pea plant with spherical seeds and a true-breeding pea plant with wrinkled seeds will produce f1 progeny with spherical seeds?

1 or 100%

Explanation:

Let the allele for seed shape be represented by S.

True breeding spherical shape seeded pea plant will have SS as genotype

True breeding pea plant with wrinkled seeds will have ss as genotype

Crossing the two: SS x ss

Progeny: Ss, Ss, Ss, Ss

Based on the assumption that spherical shape allele is dominant over wrinkle shape allele, all the F1 offspring will have spherical seeds.

Hence, the probability is 1 or 100%