In his paper, Mendel reported that he further tested his hypothesis of independe
ID: 311999 • Letter: I
Question
In his paper, Mendel reported that he further tested his hypothesis of independent assortment by planting F_2 seeds from his seed shape and color dihybrid cross and scoring the F_3 progeny. In one of these experiments, he planted 301 round, yellow F_2 seeds, allowed the plants to self-fertilize and scored the F_3 seeds produced by each plant. He observed 38 F_2 plants which produced only round, yellow seeds, 65 F_2 plants which produced all round seeds that segregated 3 yellow to 1 green, 60 F_2 plants which produced all yellow seeds that segregated 3 round to l wrinkled, and 138 F_2 plants which produced seeds in the 9:3:3:1 phenotypic ratio that he had previously observed with the F_2 seeds. Use chi-square analysis to test whether or not the observed number of genotypes in the yellow and round-seeded F_2 phenotypic class conforms to the expected number, consistent with Mendel's hypothesis of independent assortment. What is the chi-square statistic you calculated (rounded to two decimal places)? 1.52 1.67 9.48 26.88 52.33 105.12 How many degrees of freedom should you use to determine the probability that Mendel's data conforms to the expected segregation ratio from the chi-square statistic you calculated in problem 3? 1 2 3 4 5Explanation / Answer
4. Answer - Option C - 3
Degree of freedom equals number of phenotypic characters minus 1. In dihybrid cross the number of phenotypes are four and hence the degree of freedom is 4-1 = 3.