Question

Under what conditions does one expect a 1:1:1:1 ratio?

A) AABB × aabb
B) Aabb × AABB
C) AaBb × AaBb
D) AaBb × aabb
E) AAbb × aaBB

Answer 1

A 1:1:1:1 ratio is expected in a dihybrid cross of AaBb × aabb, producing offspring with genotypes AaBb, Aabb, aaBb, and aabb in equal proportions.

Step-by-step explanation:

Under the conditions given, one expects a 1:1:1:1 ratio in a dihybrid cross where the parent genotypes are AaBb × aabb. In this scenario, the AaBb parent can produce gametes with the following combinations: AB, Ab, aB, and ab. The aabb parent can only produce one type of gamete: ab. When these gametes combine, they yield offspring with genotypes AaBb, Aabb, aaBb, and aabb, each one representing a quarter of the possible combinations, hence a 1:1:1:1 genetic ratio.