Activity 9.2 NCERT Class 10 Science, Heredity and Evolution
Activity 9.2 asks us to conduct an experiment to prove that the genotypic ratio in the f2 generation is 1:2:1
We cross each of the seeds obtained in the f2 generation with a pure recessive variety to confirm the genotypic ratio.
In Mendelian inheritance, we get a phenotypic ratio of 3:1 and genotypic ratio of 1:2:1. Phenotypic ratio is easily detectable by the trait, but we can not confirm the genotypic ratio by phenotype. So to know the genotypic ratio we cross-pollinate the f2 generation with a pure recessive variety. We call this process a Test Cross.
Different genotypes give a different result with a test cross. As a result, we can now calculate the genotypic ratio.