Final answer:
In a cross using a Punnett square between a dwarf pea plant that is homozygous recessive (tt) and a tall pea plant that is heterozygous (Tt), the resulting phenotypic ratio of the offspring is 1:1, with half being tall (Tt) and the other half being dwarf (tt).
Step-by-step explanation:
When predicting the offspring of a cross between a dwarf pea plant that is homozygous recessive (tt) and a tall pea plant that is heterozygous (Tt) using a Punnett square, we place the alleles of each parent on the top and side of the grid. In this case, the dwarf parent contributes a 't' allele for each gamete since it is homozygous recessive (tt), and the tall parent can contribute either a 'T' allele or a 't' allele since it is heterozygous (Tt).
The Punnett square would show that half of the offspring will have the heterozygous (Tt) genotype, resulting in a tall phenotype. The other half will inherit the homozygous recessive (tt) genotype, resulting in a dwarf phenotype. Therefore, the phenotypic ratio of the offspring would be 1:1, tall to dwarf, respectively.