In a testcross AaBb x aabb, 90% of the progeny is like parents. Determine:
Is there any crossing over between the genes?

Explanation

To determine if there is any crossing over between the genes in the test cross AaBb x aabb, we can follow these steps:

### Step 1: Understand the Test Cross
A test cross involves crossing an individual with a dominant phenotype (but unknown genotype) with a homozygous recessive individual. In this case, we are crossing AaBb (heterozygous for both traits) with aabb (homozygous recessive for both traits).

### Step 2: Determine Expected Progeny Without Crossing Over
If there is no crossing over, the expected progeny from the test cross would be:
- Parental types: AaBb (dominant phenotype) and aabb (recessive phenotype)
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