1. What are the chances of the offspring being homozygous for round seed? R/R = ¼ = 50%
2. What are the chances of the offspring being heterozygous for wrinkled seed? r/r = 0% → 0%
3. What are the chances of the offspring being homozygous for green seed color? Y/Y = ¼ = 25%
4. What are the chances of the offspring being heterozygous for both seed shape and color? R/r Y/y = ¼ = 25%. Why? The chances of the offspring being heterozygous for both seed shape and color is 25% because ½ percent from one parent is Rr and 25% of the gametes from the other parent are rY. So, there is a 25% chance of the offspring being heterozygous for both seed shape and color.
5. What is the genotype ratio? 25% RRYY, 25% RRyy, 25% RrYY, 25% Rryy
6. What is the phenotypic ratio? 50% round, yellow seeds; 50% round, green seeds
Parent Tip: Review the logic above to help your child master the concept of dihybrid cross problems worksheet.
