Final answer:
The genotype that will predominate in the progeny when a female with a trans configuration is crossed with a double homozygous recessive male can't be determined without the recombination frequency. Parental allele combinations usually predominate, so offspring genotypes p+b and pb+ would be expected in equal proportions if crossing over is infrequent.
Step-by-step explanation:
When a female double heterozygote with a trans configuration is test crossed with a male who is double homozygous recessive, the genotypes of the offspring will depend on the recombination frequency between the genes. If the genes are closely linked and recombination is rare, the progeny will predominantly show the parental combinations of alleles: p+b+ and pb.
The Punnett square could be used to forecast the expected offspring genotypes and their proportions. Since the female is in trans configuration (p+b/pb+), each allele at one loci is linked with its recessive allele at the other loci. The homozygous recessive male will contribute only pb alleles.