Multiple Choice
Which type of genetic cross occurs when organisms that are heterozygous for two traits are crossed?
4
views
2. Mendel's Laws of Inheritance
Dihybrid Cross
Struggling with Genetics?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
In a dihybrid cross, if the resulting offspring phenotypic ratio is 1:1:1:1, what are the genotypes of the parents?
A
AAbb × aaBB
B
AaBb × aabb
C
AABB × aabb
D
AaBb × AaBb
Verified step by step guidance1
Understand that a 1:1:1:1 phenotypic ratio in a dihybrid cross typically indicates a test cross involving a heterozygous individual crossed with a homozygous recessive individual for both traits.
Recall that in a dihybrid cross, the genotypes involve two genes, each with two alleles (e.g., A/a and B/b). The heterozygous genotype is AaBb, and the homozygous recessive genotype is aabb.
Analyze the given options and identify which parental genotypes would produce offspring with a 1:1:1:1 phenotypic ratio. This ratio arises when one parent is heterozygous for both traits (AaBb) and the other is homozygous recessive for both traits (aabb).
Use a Punnett square to confirm this: crossing AaBb (heterozygous) with aabb (homozygous recessive) will produce four equally frequent genotypes (AaBb, Aabb, aaBb, aabb), corresponding to the 1:1:1:1 phenotypic ratio.
Conclude that the parental genotypes must be AaBb × aabb to produce the observed 1:1:1:1 phenotypic ratio in the offspring.
Related Videos
Related Practice
