In a tomato plant experiment, two heterozygous individuals were crossed (the details of the cross are not relevant here). The predicted Mendelian ratios for the offspring of this cross were 9 : 3 : 3 : 1 for each of the four following phenotypes: purple stem-jagged leaf edge, purple stem-smooth leaf edge, green stem-jagged leaf edge, green stem-smooth leaf edge. The observed results of the cross were not exactly as predicted. The numbers of offspring with each phenotype are provided below: Observed results of the tomato plant cross Purple stem-jagged leaf edge: 12, Green stem-jagged leaf edge: 8, Purple stem-smooth leaf edge: 9, Green stem-smooth leaf edge: 0 (a) State your null hypothesis for this investigation
