This tutorial will take you step by step through the question. Individuals with the genotypes Aa Bb CC Dd and Aa bb Cc Dd are crossed. Alleles of these four genes assort independently of one another. Step 5: Calculate the combined probability of Aa Bb Cc Dd. For the offspring genotype Aa Bb Cc Dd enter the proportions you calculated for each locus. Then, calculate the combined proportion among the offspring. Use decimals (e. g., 0.5) rather than fractions to do your calculations. probability of Aa among offspring: probability of Bb among offspring: probability of Cc among offspring: probability of Dd among offspring: combined probability of Aa Bb Cc Dd=