Answer:
4/16 (i.e. 25%)
Explanation:
A dihybrid cross is a cross between two organisms/lines/genes that are hybrids (i.e., heterozygous) for two different traits. In a standard dihybrid cross, there is a relation of complete dominance for both <em>loci</em>, i.e., there are two alleles that are completely dominant and thus mask the effects of the corresponding recessive traits. In a dihybrid cross involving two different genes that assort independently into gametes during meiosis, with dominant alleles "A" and "B" and recessive alleles "a" and "b", respectively, the expected phenotypic ratio will be 9:3:3:1 (ie. 9/16 A_B_, 3/16 A_bb, 3/16 aaB_ and 1/16 aabb), while the expected genotypic ratio of double heterozygous "AaBb" individuals will be 4/16, i.e. 25%.
Representation:
P generation >> AaBb (father) X AaBb (mother)
Gametes (for both parents) >> 1/4 AB; 1/4 Ab; 1/4 aB; 1/4 ab
F1 generation >> 1/16 AABB; 2/16 AABb; 2/16 AaBB; 4/16 AaBb; 1/16 AAbb; 2/16 Aabb; 1/16 aaBB; 2/16 aaBb; 1/16 aabb
