Which of the following is an example of a testcross?Multiple choice question.AaBb x AaBbaabb x aabbAaBb x AABBAaBb x aabb

Break Down the Problem

1. Identify the options for testcross examples: Review the given pairs:

   • AaBb x AaBb
   • aabb x aabb
   • AaBb x AABb
   • AaBb x aabb

2. Understand the testcross definition: A testcross involves breeding an individual with a dominant phenotype but unknown genotype (e.g., Aa or AABb) with a homozygous recessive individual (e.g., aabb).

Relevant Concepts

1. Testcross Characteristics: In a testcross:
   • The individual with the dominant phenotype is crossed with a homozygous recessive.
   • This determines if the dominant individual is homozygous or heterozygous based on the offspring’s phenotypes.

Analysis and Detail

1. Evaluate Each Pair:
   • AaBb x AaBb: Both are heterozygous; this cannot be a testcross.
   • aabb x aabb: Both are homozygous recessive; this is not a testcross.
   • AaBb x AABb: Not a homozygous recessive; this cannot be a testcross.
   • AaBb x aabb: Here, AaBb (dominant phenotype) is crossed with aabb (homozygous recessive). This fits the testcross definition.

Verify and Summarize

1. Conclusion: Only the pairing AaBb x aabb satisfies the conditions of a testcross, allowing us to analyze the genotype ratio of the offspring.

Final Answer

The correct example of a testcross is AaBb x aabb.