In Mendel's research, what was the primary reason for conducting test crosses?

Mendel conducted test crosses primarily to confirm the presence of recessive traits in an organism's genotype. A test cross involves mating an individual exhibiting a dominant phenotype with an individual that is homozygous recessive for the trait in question. This method is effective because the recessive traits can only appear in the phenotype if the individual being tested carries a recessive allele for that trait.

If the individual with the dominant phenotype is homozygous dominant, all offspring will show the dominant phenotype. However, if the individual is heterozygous (carrying one dominant and one recessive allele), some offspring will exhibit the recessive phenotype. Therefore, by analyzing the phenotypes of the offspring, one can deduce whether the original individual carries one or two copies of the dominant allele. This method was crucial for Mendel’s work in establishing the basic principles of inheritance and understanding how traits are passed from parents to offspring.