Final answer:
To conduct a chi-square analysis for gene linkage, the starting point is the null hypothesis, which assumes no significant deviation between observed genetic ratios and those expected by the law of independent assortment.
Step-by-step explanation:
To perform a chi-square analysis for gene linkage, we start with a null hypothesis that there is no difference between observed values and those expected based on the law of independent assortment.
The chi-square analysis is used to determine whether observed genetic ratios deviate significantly from those expected according to the null hypothesis. In the context of gene linkage, the expected values are those predicted by the law of independent assortment, which suggests that each allele combination is equally likely.
When genes are on different chromosomes, they are expected to assort independently during meiosis, appearing in different gametes 50% of the time. If genes show up in different gametes less than 50% of the time, implying they tend to be inherited together, it suggests linkage and thus a violation of the law of independent assortment. The chi-square test will compare the observed frequencies of allele combinations in offspring to the expected frequencies if the genes were indeed assorting independently.
If the chi-square statistic calculated from the data is greater than the critical value from the chi-square distribution table for the given degrees of freedom and confidence level (usually 95%), the null hypothesis is rejected, supporting the claim of gene linkage.