In corn, kernels are usually smooth due to the Su allele. The recessive su allele gives the kernel a wrinkled appearance. Likewise, kernel color in corn can either be colorless due to the recessive r allele or purple due to the dominant R allele. You wish to deduce the genotype of a smooth, purple kernel for your experiment. What are all the possible genotypes this corn kernel could be at the smooth and purple loci? What genotype and phenotype of corn should you use in order to do a testcross? What are the phenotypic ratios expected from this testcross for each of the possible mystery kernel genotypes? Solution Answering the first part of this question we need to see that there are two allele in this Corn, one for the Kernel smoothness/roughness- Su/ su allele, another is the colour Purple / colorless- R/ r. So for the corn to be genotypically contain smooth and purple color there should be both the dominant allele that is Su for smoothness and R for the purple trait, so wr can say that it has to be SuR type genotype to make smooth and purple appearance. To understand it from the use of punnet square- Totlly there will be 9 of them which can produce Smooth and Purple appearance. F2 GENERATION: SuR * sur SuR Sur suR sur * SuR Sur suR sur SuSuRR (Smooth and Purple) SuSuRr (Smooth and Purple) SusuRR (Smooth and Purple) SusuRr (Smooth and Purple) SuSuRr (Smooth and Purple) SuSurr (Smooth and colorless) SusurR (Smooth and Purple) Susurr (Smooth and colorless) suSuRR (Smooth and Purple) suSuRr (Smooth and Purple) susuRR (Wrinkled and purple) susuRr (Wrinkled and purple) suSurR (Smooth and Purple) suSurr (Smooth and colorless) susurR (Wrinkled and purple) susurr (Wrinkled and colourless) The testcross is shown above in the punnet sqaure, we need to use the dominat allele of SuR (Smoot and Purple) against recessive allele sur (Wrinkled and colorless). Phenotypic ratio will be 9:3:3:1. SuSuRR (Smooth and Purple) SuSuRr (Smooth and Purple) SusuRR (Smooth and Purple) SusuRr (Smooth and Purple) SuSuRr (Smooth and Purple) SuSurr (Smooth and colorless) SusurR (Smooth and Purple) Susurr (Smooth and colorless) suSuRR (Smooth and Purple) suSuRr (Smooth and Purple) susuRR (Wrinkled and purple) susuRr (Wrinkled and purple) suSurR (Smooth and Purple) suSurr (Smooth and colorless) susurR (Wrinkled and purple) susurr (Wrinkled and colourless).