Question

You are interested in tracking a particular trait. To begin your studies you do a dihybrid self cross. What percentage of the offspring will be dihybrids themselves

Answer 1

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 loci, 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