Final answer:
The dihybrid ratio with independent assortment of polygenes reflects a complex pattern due to multiple genes contributing to a single trait, but if two polygenes exhibit complete dominance and independent assortment, the pattern may still be calculated using the product rule as for a simple Mendelian dihybrid cross.
Step-by-step explanation:
The dihybrid ratio with independent assortment of polygenes would likely still reflect the pattern of 16 parts due to two-gene interactions where each gene follows complete dominance and independent assortment. The classic Mendelian dihybrid cross ratio is 9:3:3:1, for traits that are non-interacting and expressed in a simple dominant-recessive pattern. When considering polygenic inheritance, the expected phenotypic ratios can become more complex due to the combined effect of multiple genes contributing to a single trait.
However, if we consider a simple case with two polygenes showing complete dominance and independent assortment, one could still use the product rule to calculate expected phenotypic ratios as demonstrated with single gene dihybrid crosses. The frequencies of the individual traits would need to be determined separately and then combined to provide the overall frequencies for the dihybrid cross phenotypes.
In genetics problems, any time you see a phenotypic ratio that totals to 16, you can associate it with a two-gene interaction. This holds true if the genes are not linked and independently assort into gametes. For polygenic traits, the ratios may vary based on the number of genes involved and their mode of inheritance.