One of the standard techniques to determine whether two loci are physically close to one another on the same chromosome is to conduct a "dihybrid cross", a cross of two individuals that are heterozygous at both loci. For example, if the two loci have alleles A and a at the first locus and B and b at the second locus then crossing two AaBI individuals (where the capital alleles are known to be on the same chromosome) is performed. If the loci are not close to one another (or are on different chromosomes) then the expected frequencies of the gametes would be 1/4 AB, 1/4 Ab, 1/4 aB and 1/4 ab - leading to expected frequencies of 1/16 for each of the possible gamete combinations in the offspring. The genetics model that makes these predictions is the "model of independent assortment." Consider the following situation. At the first locus: AA homozygotes are Black, aa homozygotes are white, and the A allele is dominant to the a allele. At the second locus: BB individuals are large, bb individuals are small, and Bb individuals are intermediate in size. An experiment is conducted in which two AaBb heterozygotes are crossed to produce numerous offspring with phenotypes in the following numbers. Black large Black intermediate Black small White large White intermediate White small Observed 225 564 222 107 197 85 Perform a chi-square test to determine whether the loci are likely to be physically close to one another. What X² value do you obtain? (report to nearest 0.001) — X² = ? 2 How many degrees of freedom do you have for this X2 statistical test? 3 Choose the statement that best matches the conclusion of your t test. Your choices will be: The observed frequencies of the phenotypes are not significantly different from those predicted from a model of independent assortment (0.05 < p ). The observed frequencies of the phenotypes are not significantly different from those predicted from a model of independent assortment (0.025 < p < 0.05). df = ? The observed frequencies of the phenotypes are not significantly different from those predicted from a model of independent assortment (0.01 < p < 0.025). The observed frequencies of the phenotypes are not significantly different from those predicted from a model of independent assortment (0.001 < p < 0.01). The observed frequencies of the phenotypes are not significantly different from those predicted from a model of independent assortment (p < 0.001). The observed frequencies of the phenotypes are significantly different from those predicted from a model of independent assortment (0.05 < p ). The observed frequencies of the phenotypes are significantly different from those predicted from a model of independent assortment (0.025 < p < 0.05). The observed frequencies of the phenotypes are significantly different from those predicted from a model of independent assortment (0.01 < p < 0.025). The observed frequencies of the phenotypes are significantly different from those predicted from a model of independent assortment (0.001 < p < 0.01). The observed frequencies of the phenotypes are significantly different from those predicted from a model of independent assortment (p < 0.001).