In a dihybrid cross represented by a Punnett Square, which of the following combinations is correct?

In a dihybrid cross, which examines the inheritance of two traits, it is essential to ensure that both parents contribute a variety of alleles for both traits being studied. In the correct example, both parents are heterozygous for both traits (TtPp), allowing for a complete assortment of gametes for each trait.

When both parents are TtPp, they can produce gametes that carry a combination of the alleles: TP, Tp, tP, and tp. This results in a diverse set of offspring combinations when laid out in a Punnett Square. The correct combination demonstrates the potential for all four genotype combinations (TT, Tt, tt for the first trait and PP, Pp, pp for the second trait) to appear in the offspring, thus reflecting the principles of Mendelian genetics.

Using parents that differ in only one of the traits or that are homozygous will limit the variety of combinations in the offspring, failing to exemplify a true dihybrid cross. This is why the combination involving both parents as TtPp is the appropriate selection for a classic dihybrid cross scenario.