Final answer:
The configuration of alleles in the heterozygous parent of a dihybrid cross is determined by the phenotypic proportions of the offspring. Given the proportions of AB and aB phenotypes, the alleles are likely in trans configuration. Without complete data, the exact configuration is speculative.
Step-by-step explanation:
The question pertains to the configuration of the alleles in a dihybrid cross where one parent is heterozygous (AaBb) and the other is homozygous recessive (aabb). The observed phenotypic proportions suggest incomplete linkage or codominance, where the offspring display a different ratio than the expected 9:3:3:1 for a simple Mendelian dihybrid cross. For the heterozygous parent, each trait is inherited independently according to Mendel's law of independent assortment, which predicts that the F1 gametes will have the genotypes AB, aB, Ab, and ab.
To determine the configuration of the heterozygous parent, we must look at the given phenotypic proportions. If the alleles were in a coupling configuration (in cis), we would expect more offspring with either both dominant or both recessive traits. The fact that we see more AB than aB offspring suggests that the alleles are in a repulsion or trans configuration (A and b are on one chromosome, while a and B are on the other). This leads to a higher probability of producing gametes with either A or B, but not both. However, without the complete ratio or information about recombination frequencies, determining the exact configuration can be more speculative.